Download 26. Metering Code Committee - Assam Electricity Regulatory

ASSAM ELECTRICITY REGULATORY COMMISSION
GUWAHATI, ASSAM
METERING CODE FOR ASSAM GRID REGULATIONS
(Part V of Assam Grid Code)
Draft for Comments
Version 1.1
Assam Electricity Regulatory Commission
Sarumatoria
Swahid Dilip Huzuri Path,
P.O. Sachivalaya, Dispur,
GUWAHATI -781006
Metering Code for Assam Grid
Page 1
April 2004
METERING CODE FOR ASSAM GRID REGULATIONS
REVISIONS SUMMARY
REVISION
NUMBER
Metering Code for Assam Grid
DATE ISSUED
SECTIONS REVISED
Page 2
April 2004
TABLE OF CONTENTS
1.
SHORT TITLE, COMMENCEMENT AND INTERPRETATION:- .................................................................. 5
1.
INTRODUCTION ................................................................................................................................................ 6
2.
OBJECTIVE ......................................................................................................................................................... 6
3.
SCOPE.................................................................................................................................................................. 6
4.
APPLICABILITY ................................................................................................................................................ 6
5.
REFERENCE STANDARDS .............................................................................................................................. 7
6.
DEFINITIONS ..................................................................................................................................................... 7
7.
OWNERSHIP ..................................................................................................................................................... 13
8.
RIGHT TO INSTALL ENERGY METERS ...................................................................................................... 13
9.
FACILITY TO BE PROVIDED ON METERING LOCATIONS ..................................................................... 13
10.
ACCESS TO EQUIPMENT AND DATA ..................................................................................................... 13
11.
OPERATION AND MAINTENANCE OF THE METERING SYSTEM ..................................................... 13
12.
TYPE OF METERS AND METERING CAPABILITY................................................................................ 13
13.
MINIMUM TECHNICAL REQUIREMENTS FOR ENERGY METER...................................................... 14
14.
MINIMUM TECHNICAL REQUIREMENT FOR CURRENT TRANSFORMER (CT) ............................. 16
15.
MINIMUM TECHNICAL REQUIREMENT FOR VOLTAGE TRANSFORMERS (VT) .......................... 17
16.
MINIMUM TECHNICAL REQUIREMENT FOR REMOTE TRANSMITTING UNIT (RTU) ................. 17
17.
TESTING ARRANGEMENT ........................................................................................................................ 18
18.
METER READING, DATA COLLECTION AND DATA DOWNLOADING ............................................ 18
19.
RIGHTS OF ACCESS TO METERING DATA ............................................................................................ 19
20.
SYSTEM FOR JOINT INSPECTION, TESTING, CALIBRATIONS .......................................................... 19
21.
SEALING ....................................................................................................................................................... 20
22.
ASSESSMENT OF CONSUMPTION OF DEFECTIVE AND/OR STUCK-UP METER ........................... 20
23.
REPLACEMENT OF DEFECTIVE OR STUCK-UP METER ..................................................................... 20
24.
INTERFACE METERING ARRANGEMENT ............................................................................................. 20
25.
ABT, TWO PART AND TOD TARIFF CAPABILITY ................................................................................ 23
26.
METERING CODE COMMITTEE ............................................................................................................... 23
27.
MECHANISM FOR DISPUTE RESOLUTION ............................................................................................ 24
28.
DYNAMIC CODE ......................................................................................................................................... 24
Metering Code for Assam Grid
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General Overview of Metering Code for Assam Grid
General
The metering code provides uniform policies and procedures in respect of electricity metering in
different parts of Power System. The uniform policy, procedures and practices included in
metering code covers the ownership, installation, operation & maintenance of metering system,
minimum acceptable specification of meters, CTs ,PTs and CT/PT set etc. The metering Code
prescribes the testing & calibration procedure and also periodicity. The metering code covers
metering system for Assam Gridco, Generating Companies, Distribution Licensees and also for
the open access customers on intra state Transmission system and EHV Consumers of
Distribution Licensees directly connected to intra State Transmission System.
The Electricity Act, 2003 prescribes that for proper accounting and audit in the generation,
transmission and distribution or trading of electricity, the CEA may direct the installation of
meter by a generating company or licensee at such stage of generation, transmission or
distribution or trading of electricity and at such locations of generation, transmission or
distribution or trading, as it may deem necessary.
The Act further provides that CEA under section 73 (e) will specify the conditions for
installation of meters for transmission and supply of electricity This metering code therefore will
require review after the CEA issue regulations on conditions for installation of meters for
transmission and supply of electricity.
Legal Provisions relating to Metering
E Act 2003 Section 55- Use, etc of Meters
(1) No licensee shall supply electricity, after the expiry of two years from appointed date,
except through installation of a correct meter in accordance with regulations to be made
in this behalf by the Authority:
Provided that licensee may require the consumer to give him security for the price of a
meter and enter into an agreement for hire thereof, unless the consumer elects to
purchase a meter:
Provided further that the State Commission may, by notification, extend the said period
of two years for a class or classes of persons or for such area as may be specified in that
notification.
(2) For proper accounting and audit in the generation, transmission and distribution or
trading of electricity, the Authority may direct the installation of meter by a generating
company or licensee at such stage of generation, transmission or distribution or trading
of electricity and at such locations of generation, transmission or distribution or trading,
as it may deem necessary.
(3) If a person makes default in complying with provisions contained in this section or the
regulations made under sub-section (1), the Appropriate Commission may make such
order as it think fit for requiring the default to be made good by the generating company
or licensee or by any officers of a company or other association or any other person who
is responsible for its default.
E Act 2003 Section 73 (e)
The Central Electricity Authority to specify the conditions for installation of meters for
transmission and supply of electricity.
Metering Code for Assam Grid
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April 2004
Assam Electricity Regulatory Commission
METERING CODE FOR ASSAM GRID REGULATIONS
Regulation No. AERC/
/2004
Dated
In exercise of powers under Sections 181 of the Electricity Act, 2003 read with Section
55 and all powers enabling it in that behalf, the Assam Electricity Regulatory Commission
hereby frames the following Regulations as appended:-
1.
Short title, commencement and interpretation:-
1.1
This Regulation may be called the Assam Electricity Regulatory Commission (Metering
Code for Assam Grid) Regulations, 2004.
1.2
This Metering Code for Assam Grid Regulation applies to all intra-State Transmission
System participants, including
1. Transmission Licensees
2. Generating Stations connected to intra State Transmission System
3. Distribution Licensees connected with intra State Transmission System
4. EHV Consumers of Distribution Licensee directly connected to intra State
Transmission System
5. Open access customers availing open access on intra state Transmission system
6. Captive Generators connected to intra State Transmission System
1.3
This Regulation extends to the whole of the State of Assam
1.4
This Regulation shall come into force with effect from 10th June 2004.
Metering Code for Assam Grid
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April 2004
METERING CODE FOR ASSAM GRID
1.
Introduction
1.1
The code prescribes a uniform policy in respect of electricity metering in the intra State
Transmission System amongst the utilities i.e. Assam Gridco, Generating Companies,
Distribution Licensees and also for the open access customers on intra state
Transmission system and EHV Consumers of Distribution Licensees directly connected
to intra State Transmission System.
1.2
This code shall be an integral part of the State Grid Code prepared under section 86 (1)
(h) of Electricity Act 2003.
2.
Objective
The objective of the code is to define minimum acceptable metering standards which will
affect proper metering of the system parameters for the purpose of accounting,
commercial billing and settlement of electrical energy and will also provide information
which enable to operate the system in economic manner consistent with license
conditions by licensee and Assam Gridco to effect management of generation and
transmission in a safe and economical manner.
3.
Scope
3.1
The scope of the code covers the practices that shall be employed and the facilities that
shall be provided for the measurement and recording of various parameters like
active/reactive/apparent power/energy, power factor, voltage, frequency etc.
3.2
The code sets out or refers to the requirements of metering at generating stations, substations and interfaces for Tariff and Operational metering.
3.3
The code also specifies the requirement for calibration, testing and commissioning of
metering equipments viz. energy meters with associated accessories, current transformers
and voltage transformers. The code broadly indicates the technical features of various
elements of the metering, data communication and testing system, the procedure for
assessment of consumption in case of defective and stuck-up meters and also lays down
guidelines for resolution of disputes between different agencies.
3.4
The Metering Code shall be effective from the date as notified by the Commission and
accordingly the concerned licensees shall have obligation for its implementation.
4.
Applicability
4.1
This Metering Code for Assam Grid shall apply to:
7. Transmission Licensees
8. Generating Stations connected to intra State Transmission System
Metering Code for Assam Grid
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9. Distribution Licensees connected with intra State Transmission System
10. EHV Consumers of Distribution Licensee directly connected to intra State
Transmission System
11. Open access customers availing open access on intra state Transmission system
12. Captive Generators connected to intra State Transmission System
5.
Reference Standards
5.1
The following Indian Standards (amended up to date) shall be applicable as relevant to
meters and associated equipment
Sr.
No.
i.
ii.
Standard
Number
IS 13779
IS
i 14697
Standard Title
AC Static Watt-hour Meters for Class 1 & 2
AC Static Transformer Operated Watt-hour and VAr-hour Meters,
Class 0.2S and 0.5S
iii. IS 2705
Indian Standard for Current Transformers
iv. IS 3156
Indian Standard for Voltage Transformers
v.
IS 9348
Indian Standard for Coupling Capacitors and Capacitor Divider
vi. IS 5547
Indian Standard for Capacitor Voltage Transformer
vii. CBIP Technical Specification for AC Static Electrical Energy Meters
Report - 88
viii. CBIP Technical Specification for Common Meter Reading Instrument
Report - 111
ix. IS 9000
Basic Environmental Testing Procedures for Electronic & Electrical
items
5.2
The following International Standards (amended up to date) can be applicable as relevant
to meters and associated equipment not complying to Indian Standards or not
manufactured in India:
Sr.
No.
i.
Standard
Number
IEC
i
687
ii.
IEC 1036
iii.
IEC 1268
6.
Standard Title
Specification for AC Static Watt-hour Meters for Active Energy
(Classes 0.2S and 0.5S)
Alternating Current Static Watt-hour Meters for Active Energy
(Classes 1 & 2)
Alternating Current Static Watt-hour Meters for Reactive Energy
(Classes 2 & 3)
Definitions
In the Metering Code for Assam Grid, the following words and expressions shall, unless
the subject matter or context otherwise requires or is inconsistent therewith, bear the
meaning given hereunder:
6.1
Active Energy
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Active Energy means the electrical energy produced, flowing or supplied by an electrical
circuit during a time interval, and being the integral of the instantaneous power with
respect to time, measured in units of watt hours or standard multiples thereof.
Unless otherwise qualified, the term “energy” refers to active energy.
6.2
Active Power
Active Power means the product of voltage and the in-phase component of alternating
current measured in units of watts and standard multiples thereof.
6.3
Apparent Energy
Apparent Energy means the integral of the Apparent Power with respect to time. It is
measured in Volt Ampere hour and standard multiple thereof.
6.4
Apparent Power
Apparent Power means the product of the root-mean-square (RMS) or effective value of
the current and the root-mean-square value of the voltage. For AC circuits or systems, it
is the square root of the sum of the squares of the active and reactive power and is
measured in kilo volt-ampere (KVA) or multiples thereof.
6.5
Assam Gridco
Assam Gridco means Assam Electricity Grid Corporation Limited registered under the
Companies Act, 1956. Assam Gridco is successor entity of ASEB under the provisions
of section 131 of the Act and is the State Transmission Utility for Assam as notified by
the State Government under section 39 of the Act.
6.6
Base Computer System (BCS)
BCS means Base Computer System meant to handle the data downloaded from meters
through CMRI or through remote communication network, converts downloaded raw
data into standard output format (e.g. ASCII, CSV) and processes data for various
calculations, analysis and display.
6.7
Data Processing System (DPS)
Data Processing System means a Computer System meant for receiving data
manually/downloaded through CMRI or through remote communication network,
converts downloaded raw data into standard output format (e.g. ASCII, CSV) and
processes data for various calculations, analysis and display.
6.8
Centralized Data Collection Centre (CDCC)
The centre which is responsible to collect, collate and process the energy meter data for
various applications like energy accounting and auditing, energy billing, transmission
system loss calculations and power purchase bill reconciliation.
6.9
Commission/AERC
Metering Code for Assam Grid
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“Commission” or “AERC” means the Assam Electricity Regulatory Commission
constituted under section 17 of the Electricity Regulatory Commissions Act, 1998 and
which continues to be so under section 82 of the Electricity Act, 2003 (no.36 of 2003).
6.10
Common Meter Reading Instrument (CMRI or MRI)
CMRI means a common meter reading instrument with necessary accessories capable of
downloading data/information from various makes of AC static energy meters when
loaded with the corresponding meter specific downloading software(s) called meter
reading instrument program(s).
(Note: The CMRI can extract information about energy data, load survey data, billing
parameters, meter status, meter anomaly and tamper data from the memory of the meter
and store for retrieval at a later stage.)
6.11
Demand Integration Period
Demand Integration Period means the period over which active power, reactive power or
apparent power is integrated to produce energy value for averaging. For settlement
purpose under ABT, each Demand Integration Period shall be of 15 minutes duration,
which shall commence from 00.00 hours. Any two successive Demand Integration
Periods can contain time intervals, which may be non-overlapping (in case of “fixed time
window” principle of measurement) or overlapping (in case of sliding time window”
principle of measurement), is used for integration of demand.
6.12
Demand Values
(a) Demand value in terms of energy: Energy demand means active energy, reactive
energy or apparent energy drawn during any demand period, one of which shall
commence from 00.00 hours.
(b) Demand value in terms of power: Power demand means active power, reactive power
or apparent power drawn during any demand period, one of which shall commence
from 00.00 hours.
6.13
Distribution Licensee
Distribution Licensee means a licensee authorised by the Commission under section 14
of the Act to operate and maintain a distribution system for supplying electricity to the
consumers in his area of supply and includes ASEB and any of its successor entity
deemed with a distribution license under the provisions of section 131 of the Act.
6.14
Distribution System
Distribution System means the system of wires and associated facilities between the
delivery points on the transmission lines or the generating station connection and the
point of connection to the installation of the consumers.
6.15
Generating Company
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Generating Company means any company or body corporate or association or body of
individuals, whether incorporated or not, or artificial juridical person, which owns or
operates or maintains a generating station.
6.16
Instrument Transformers
Current Transformer (CT) or Voltage Transformer (VT) and composite CT-PT set. The
term VT is used to cover either Potential Transformer (PT) or Capacitive Voltage
Transformer (CVT).
6.17
Load Survey Data
Load survey data is a database of load values defined in terms of Watt, VAr or VA (or
multiples of thereof) during each predefined interval of time.
6.18
Meter
Meter means a device for measurement of bi-directional active energy, reactive energy,
apparent energy, active power, reactive power (lag/lead), apparent power, currents,
voltages, power factor, frequency and any other electrical parameter derived out of these
measurements. Meter shall be capable to record the various parameters as may be
required for a particular category of the consumers on the basis of tariff applicable from
time to time.
6.19
Main Meter and Check Meter
The primary meter used for billing purpose is named as Main Meter. The check meter is
used as back-up to main meter for billing purpose, in case main meter fails or operates
erroneously or shows error beyond permissible limits.
6.20
Metering System
Metering System means set of meters, measurement transformers (CTs & VTs), metering
protection equipment including alarms, circuitry and their associated data collection
outstations and wiring which are part of the measuring equipment at or relating to a site.
CT means current transformers and term VT is used to cover either PT or CVT.
6.21
Metering Point
Actual metering point means the physical location of current and voltage sensing devices
(i.e. CTs, VTs) and meters at which electricity is metered.
6.22
MMI (Man Machine Interface)
Devices / software used by operating personnel to interact with computerized system /
instrumentation etc.
6.23
Assam Gridco
Assam Gridco means Assam Electricity Grid Corporation Limited registered under the
Companies Act, 1956. Assam Gridco is successor entity of ASEB under the provisions
Metering Code for Assam Grid
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April 2004
of section 131 of the Act and is the State Transmission Utility for Assam as notified by
the State Government under section 39 of the Act.
6.24
Operational Metering
Metering equipment and associated accessories (excluding any tariff metering) installed
in the sub-station or generating station primarily for:
6.25
(a)
Operational and System Control purposes
(b)
Monitoring and Manual Recording purposes
(c)
Auditing and accounting of energy
Overall Accuracy
The combined accuracy of meter, associated instrument transformers and cabling for a
given metering system.
6.26
Open Access
Open Access means the non-discriminatory provision for use of transmission lines or
distribution system or associated facilities with such lines or system by any licensee or
consumer or a person engaged in generation in accordance with the regulations specified
by the Appropriate Commission.
6.27
Open Access Consumer
Open Access Consumer means a consumer who is eligible to receive supply of
electricity from a person other than the distribution licensee of his area of supply.
6.28
Open Access Customer
“Open Access Customer” means a person using or intending to use the transmission
system or the distribution system or both of the licensees in the state for transmission or
wheeling of electricity in the State.
6.29
Power factor
Power factor shall have the meaning as assigned to it in tariff order for supply of
electricity.
6.30
Protocol
Protocol is the software implemented to exchange the information with external device or
equipment through interfacing communication port.
6.31
Reactive Power
Reactive Power means the product of voltage and current and the sine of the phase angle
between them measured in units of volt amperes reactive and standard multiples thereof.
6.32
Reactive Energy
Metering Code for Assam Grid
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April 2004
Reactive Energy means the integral of the Reactive Power with respect to time. It is
measured in volt-amperes reactive hours and standard multiple thereof.
6.33
Remote Transmitting Unit (RTU)
RTU means a unit for data transmission in digital and sequential mode i.e. to transmit
low level analogue / digital signals from transducers, switches, relays etc. connected to it
and to transmit received signal to devices connected to it.
6.34
Simultaneous Maximum Demand (SMD)
For a given demand period, sum of individual demand across all interface points in a
Distribution System gives simultaneous demand of a Distribution Licensee for a given
period. SMD means the maximum demand value out of all such simultaneous demands
for a month (i.e. maximum demand value out of 4 x 24 x 30 = 2880 periods in a month
for demand interval of 15 minutes)
6.35
Intra State Transmission System
Intra State Transmission System means the system of EHV electric lines and electrical
equipment operated and/or maintained by transmission licensee for the purpose of the
transmission of electricity among generating stations, external interconnections,
distribution systems and any other user connected to it.
6.36
State Transmission Utility (STU)
The utility notified by the Government of Assam as State Transmission Utility under
section 39 of the Electricity Act, 2003. State Transmission Utility (STU) owns and
operates the transmission system of the State. Assam Electricity Grid Corporation
Limited (Assam Gridco) is the State Transmission Utility for Assam as notified by the
State Government.
6.37
Tariff Metering or Commercial Metering
The energy measurement system comprising of metering equipments and associated data
collection devices, based on which the energy supplying entity raises bills payable by the
energy receiving entity or consumer.
6.38
TOD Tariff or TOU Tariff
TOD stands for Time Of Day and TOU stands for Time Of Use, which means different
tariff during different usage time in a day.
6.39
User
User means a person, including generating companies, Distribution Licensee and open
access consumers, open access generators, any other transmission licensees or traders in
the state of Assam who uses the intra State Transmission System and who must comply
with the provisions of the Grid Code.
All other words and expressions used herein and not defined herein have the meanings
respectively assigned to item in the Act, the Grid Code or Indian Electricity Grid Code
(IEGC).
Metering Code for Assam Grid
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April 2004
7.
Ownership
The ownership of the metering system shall be as provided in relevant agreement
governing exchange of power and if no agreement exists than the ownership of the
metering system shall belong to the agency in whose premises the metering equipment is
physically located. However, the responsibility of safety of the metering system is of the
agency in whose premises the metering equipment is physically located.
8.
Right to Install Energy Meters
Each constituent agency shall extend necessary assistance to the other for installation of
the meters and RTUs by providing required access to their premises and equipments. As
and when required by the utility, the constituent/agencies shall enable the representatives
of the utility with advance notice, to access, inspect, replace, test etc. any of the meters
and RTUs for any utility installed in their premises.
9.
Facility to be provided on Metering Locations
Each constituent agency shall make available the required space for installation of
metering equipment in their premises and provide required outputs of the specified
current and voltage transformers to facilitate installation of Meters, RTUs and associated
equipment in their premises. Necessary auxiliary supply shall be extended up to the
metering system, if meter can be powered by only external supply.
10.
Access to Equipment and Data
Each constituent of the agency (Utility) on request with advance notice, shall grant full
right to install metering equipments and RTUs for other agency’s employees, agents/duly
authorized representative for inspecting, testing, calibrating, sealing, replacing the
damaged equipment, collecting the data, joint reading recording, and other functions
necessary and as mutually agreed.
11.
Operation and Maintenance of the Metering System
The operation and maintenance of the metering system includes proper installation,
regular maintenance of the metering system and RTUs, checking of errors of the CTs,
VTs and meters, proper laying of cables and protection thereof, cleaning of
connections/joints, checking of voltage drop in the CT/VT leads, condition of meter box
and enclosure, condition of seals, regular/daily reading meters and regular data retrieved
through CMRI and BCS, attending any breakdown/fault on the metering system etc.
12.
Type of Meters and Metering Capability
12.1
The meters to be used shall be suitable for measurement of commercial transactions
between the utilities according to applicable tariffs. The meters shall be all electronic
(static) poly phase tri-vector type having facility to measure active, reactive and apparent
energy/power in all four quadrants i.e. a true import export meter. All inter utility trade
meters shall be bi-directional while capacitor bank meters and sub-station aux. meters
shall be unidirectional if, bi-directional meters already exist, these will not be changed.
Metering Code for Assam Grid
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12.2
The frequency based energy meters suitable for Availability Based Tariff (ABT) shall be
provided at such interface points, wherever the energy exchange is based on ABT
according to CERC/AERC regulations/ Orders.
12.3
The various standards of metering equipment as given in Table–1, while detailed
specifications of meters are indicated at Annexure-1.
Table–1
Sr.
Particulars
No.
1
(1)
Main
Meter
2
Back up
Meter
3
Capacitor
Bank Meter
4
Substation
Auxiliary
Meter
5
InterDiscoms
Meter
6
Secondary
Back up
Meter
7
8
Accuracy class
(a)
Meter
0.2 S
0.5 S
0.5 S
1.0
0.5 S
0.5 S
(b)
CTs
0.5
Existing
Existing
Existing
Existing
Existing
0.5 /1.0
0.5 /1.0
0.5 /1.0
0.5 /1.0
0.5 /1.0
Existing
Existing
Existing
Existing
Existing PTs
0.5 /1.0
0.5 /1.0
0.5 /1.0
0.5 /1.0
0.5 /1.0
Existing
Existing
Existing
Existing
(c)
PTs / CVTs
0.5
(d)
CT-PT sets for
33kV & 11kV
feeders
0.5
(2)
Existing
Salient aspect of
meters
(a)
Phase angle and
ratio error
compensation of
CTs & PTs
(b)
Communication
port
Not to be
provided
Not to be
provided
Not to be
provided
Not to be
provided
Not to be
provided
Not to be provided
(i)
Communication
optical port
Yes
Yes
No
No
Yes
Yes
(ii)
Communication
port for remote
reading
Yes
Yes
No
No
Yes
Yes
(3)
Whether an Import
& Export both
features are
required
Yes
Yes
Yes
No
Yes
Yes
(4)
Meter memory for
75 days
Yes
Yes
No
No
Yes
Yes
13.
Minimum Technical Requirements for Energy Meter
13.1
Operating System Parameters (for balanced and unbalanced load):
(a) Operating Voltage Range: The meter shall work satisfactorily on 110 Volts AC
(Line-Line) or 415 Volts AC (Line-Line) with variation range of -40% to +20%.
(b) Operating Frequency Range: The meter shall work satisfactorily on 50 Hertz with
variation range of -5% to +5%.
(c) Operating Power Factor Range: The meter shall work satisfactorily over a power
factor range of zero lag to unity to zero lead.
13.2
Measuring Elements:
Metering Code for Assam Grid
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April 2004
13.2.1 The meter shall be 3 phase 4 wire type, capable to record and display import and
export kWh, kVArh, kVAh and maximum demand in kW and kVA for 3 phase 4
wire AC balanced/unbalanced load for a power factor having range of zero
lagging to unity to zero leading in all 4 quadrants. In addition, meter shall also be
capable of displaying, on demand, the present status of supply/load, missing
potential, CT polarity, current unbalance, anomaly occurrence and logging of
occurrences as well as load survey data etc. which shall be down loaded to a user
friendly “Basic Computer Software” (BCS) through portable data collection
devices or CMRI which shall be connected to optical communication port of the
meter. Meter shall be equipped with self-diagnostic features also and be capable
of recording average values based on their integration on time base for kWh,
kVArh, kVAh for at least 75 days. Meter shall be capable of measuring
fundamental as well as total energy including harmonics separately
13.2.2 Energy measurement during demand period will be such that sampling in the
meter is synchronized with the end of the time block otherwise energy measured
in a demand period but not stored in that period shall be carried forward. An LED
glow or pulse output coincident with end of each demand period need be
provided in the meter so as to ensure that demand integration coincided the preset
time block.
13.3
Display
Present meter status, real time and date, cumulative energy registers, voltage, currents,
power factor, present demand, frequency and meter serial number shall be available on
demand through push button. Any interrogation/read operation shall not delete or alter
any stored meter data.
13.4
Memory
(a)
Numerical values of voltage/current, power factor and cumulative energy registers as
well as anomalies/tempered details alongwith date and time of logging of and
restoration of anomalies (subject to the meter memory space) shall be logged in the
meter memory and shall be available for retrieving with the help of the data collection
devices (CMRI) through meter optical port and down loading to BCS.
(b)
Memory in a static tri-vector meter shall not get ‘erased’ after reading or retrieving of
data through MRI. Data shall be retained for a minimum of 75 days or shall not get
erased from meter until replaced by fresh data. However, desired data can be erased
from MRI, when memory of an MRI becomes full after downloading of readings of a
number of meters, as there is fixed space made available in MRI for:
(i) Energy registers.
(ii) Load survey data.
(iii) Anomaly data etc.
When a fresh data is logged in the memory, the oldest data shall disappear automatically.
13.5
Test terminal blocks
The test terminal blocks shall be provided on all meters to facilitate testing of meters in
service. Main & back up meters of inter state / major generating stations shall be having
the feature of draw out type modular units and shall have automatic CT short circuiting
so that meter can be taken out for testing without shut down requirements.
Metering Code for Assam Grid
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13.6
Meter Power Supply
Meters of inter state / major generating stations shall be capable of powered with 230
volt alternating current auxiliary supply and 110 volt or 220 volt DC supply of the
substation so that metering core of PT/CVT is never loaded and in case of shut down on
feeder/breaker, meter can be interrogated locally or remotely. It will normally be
powered by AC auxiliary supply and will be switched over to DC supply only when AC
auxiliary supply fails.
13.7
Battery back-up
The meter shall have battery back up (2 years), for its Real Time Clock (RTC).
13.8
Meter Programmability
The meters shall be equipped with necessary hardware/software to suit tariff
requirements such as ABT, TOD, two-part tariff based on SMD as may be called for
from time to time.
13.9
Earthing System:
The metering system shall be suitable for solidly earthed power system.
13.10 Meter Box:
The meter box wherever required shall confirm to the degree of protection not less than
IP-51 as stipulated in IS 12063, and shall be capable of satisfactory operation in an
indoor, non-air conditioned installation.
13.11 Installation and Mounting:
The meter shall be suitable for install indoor or outdoor application. The meter can be
mounted in dust proof, lockable and tamper proof panel or rack or metal box, as per
requirement and site condition, conforming to minimum IP-31.
The metering system shall have facility of CT shorting when the meter module is
withdrawn or dismantled.
14.
Minimum Technical Requirement for Current Transformer (CT)
14.1
Three single-phase type current transformers shall be used for 3 phase 4 wire and 3 phase
3 wire measurement system. The secondary current rating of the CTs shall be 1 ampere
particularly for 220 kV and 132 kV measurements. For other voltage 1 Amp. or 5 ampere
may be employed.
14.2
The current transformers shall have dedicated core for metering and wherever feasible,
the cores feeding to main meters and check meters shall be separate. The errors of the
current transformers shall be checked in the laboratory or at site. However if such
facilities are not available, CT test certificates issued by Government test house or
Government recognized test agency shall be referred to.
14.3
The total burden connected to each current transformer shall not exceed the rated burden
of CT. Total circuit burden shall be kept close to rated burden of CT for minimum error.
Metering Code for Assam Grid
Page 16
April 2004
15.
Minimum Technical Requirement for Voltage Transformers (VT)
15.1
Either Electromagnetic Voltage Transformers (EVT) or Capacitive Voltage transformer
(CVT) may be used for metering purpose. Generally, term VT is used to cover either
EVT or CVT. The secondary voltage per phase shall be 110/3 volts or 415/3 volts.
Either dedicated VTs or dedicated core of VTs shall be provided for metering and that
wherever feasible, VTs (or their cores) feeding to main meters and backup/check meters
will be separate. Fuses of proper rating shall be provided at appropriate locations in the
VT circuit.
15.2
The errors of the VTs shall be checked in the lab or at site. However if such facilities are
not available, VT test certificates issued by Government test house or Government
recognized test agency should be referred to.
15.3
The total burden connected to each VT shall not exceed the rated burden of VT. Voltage
drop in VT leads shall be within the permissible limits.
15.4
The current transformers and voltage transformers shall meet the requirements as per the
relevant standards. Where a combined CT/PT unit is provided, the accuracy shall be as
specified under relevant IS.
15.5
Minimum acceptable specification are enclosed at following Annexures:
1
Current Transformers
Annexure-2 A
2
CVTs
Annexure-2 B
3
Single Phase 220 & 132 kV VTs
Annexure-2 C
4
33 kV & 11 kV VTs
Annexure-2 D
5
33 kV CTPT Sets
Annexure-2 E
16.
Minimum Technical Requirement for Remote Transmitting Unit
(RTU)
16.1
Following data (instantaneous system parameters) shall be made available through
transducers and RTUs from selected individual stations to sub-load despatch centre and
load despatch centre continuously.
(a) MW (Import/export).
(b) MVAr (Lag plus lead).
(c) Voltage.
(d) Current.
(e) Frequency.
(f) The status of various isolators, circuit breakers and transformer tap positions.
16.2
Wherever meters have the capability of transmitting various parameters to SLDC / sub
LDC independent RTUs & Transducers may not be provided and meters at such
locations can duel function of Metering as well as RTU.
a. The accuracy of the transducers shall be 0.2% of span.
Metering Code for Assam Grid
Page 17
April 2004
b. The transducers and RTU’s shall conform to relevant international / national
standards.
c. The transducers shall be 3 phase 4 wire type for MW and MVAr measurement
purposes.
16.3
Single transducer giving output of MW, MVAr, voltage, frequency and ampere shall be
preferred in place of individual transducers for each metering point. The transducers
shall be connected to 0.2 class CTs and VTs and housed inside the meter box of the
check meter meant for metering purpose.
16.4
Since the above metering scheme is for commercial metering purpose therefore the
complete CT wiring including energy meter, meter test terminal block and transducers
shall be housed in the metering cubicle which shall be kept sealed. The output of the
transducers shall be connected to RTU through screened signal cable. The RTUs shall be
located in the PLCC room. The size of the CT & VT cable to the transducer shall be
same as that provided in the metering circuit.
16.5
The various data collected by transducers and fed to RTU shall be processed in the RTU
and output will be provided in digital telegraphic form. Transmission of these data to the
load despatch centre can be through any of the information link like Radio frequency,
PLCC (Power Line Carrier Communication), PSTN (Public Switched Telephone
Network), VSAT, Mobile and other means of Telemetering like private network of
Assam Gridco or low power radio. The data shall be again processed at load despatch
end in Data Concentrator Unit and converted to analog data and displayed on the monitor
screen. The RTU shall be utilized for monitoring and also for remote control of feeders /
breakers located at remote sub-stations.
16.6
The supplier should make format/protocol of data retrieval & data telex known to owner.
17.
Testing Arrangement
17.1
Two types of test facilities shall be available:
(a)
Automatic meter test bench with high accuracy, static source and 0.02S class electronic
reference standard meter (RS Meter) shall be used for testing and calibration of meters.
Meter Testing Laboratories duly equipped with testing benches and other equipments
shall be established at suitable locations for testing and calibration of meters by Assam
Gridco. The Meter Testing benches with 0.02-class reference standard shall also be used
for checking and calibration of portable testing equipments.
Portable test set with static source and electronic reference meter of 0.1 class shall be
used for verification and joint testing of accuracy of static tri-vector meters at site on
regular/routine basis.
(b)
17.2
Separate test terminal blocks for testing of main and check meters shall be provided so
that when one meter is under testing, the other meter continues to record actual energy
during testing period. Where only one/main meter exists, an additional meter shall be put
in circuit to record energy during the testing period of the main meter so that while the
main meter is under testing, the other meter can record energy during the period of meter
under testing.
18.
Meter Reading, Data Collection and Data Downloading
18.1
The Assam Gridco and concerned Generating Companies /Distribution Licensees shall
jointly read the meters through their authorized representatives on 1st of every month at
12.00 Hrs. / retrieve meter reading data using CMRI. Wherever meters are in position or
Metering Code for Assam Grid
Page 18
April 2004
in operation the tele-metered data shall be retrieved from the optical communication port
of the meter.
18.2
Where a smart meter has been installed for an open access consumer connected to the
transmission system, the Distribution Licensee will be required to keep a metering
database of the metering readings for the consumer for:
(i) 13 months in an accessible format;
(ii)5 years in archive.
19.
Rights of access to metering data
19.1
The only persons entitled to access to metering data from a metering installation are:
(i) The Distribution or Transmission Licensee who is responsible for the metering installation;
(ii)The State Load and Dispatch Centre;
(iii)The Transmission Licensee;
(iv)The consumer of electricity or the generator of electricity at the metering installation as the
case may be;
(v)Any other person who currently has an agreement to supply electricity to the consumer
associated with that metering installation. In relation to sub-clause (v), the person must
present a written authorisation from the consumer to the Distribution Licensee before the data
is to be provided; and
(vi)The Commission but only when such information is required for an investigation.
20.
System for Joint Inspection, Testing, Calibrations
20.1
The metering system located at metering points between Generating Companies, Assam
Gridco and Distribution Licensees shall be regularly inspected at least once in a year or
at an interval lesser than 1 year as mutually agreed jointly by both the agencies involved
for dispatch and receipt of energy. Since the static tri-vector meters are calibrated
through software at the manufacturers’ works, only accuracy of the meters and
functioning shall be verified during joint inspection and certified jointly by both the
agencies. To cover for loss of time, spare meters shall always be kept available with the
owner of the meter/metering point. After testing, the meter shall be properly sealed and
a joint report shall be prepared giving details of testing work carried out, details of old
seals removed and new seals affixed, test results, further action to be taken (if any) etc.
The agency in whose premises the meter is located shall be responsible for proper
security, protection of the metering equipment and sealing arrangement.
20.2
Joint inspection shall also be carried out as and when difference in meter readings (so
corrected) exceeds the sum of maximum error as per accuracy class of main and check
meter. The meters provided at the sending end as well as at the receiving end shall be
jointly tested/calibrated on all loads and power factors as per relevant standards through
static phantom load.
Metering Code for Assam Grid
Page 19
April 2004
21.
Sealing
21.1
Tariff metering systems shall be jointly sealed by the authorized representatives of the
concerned parties as per the procedure agreed upon.
21.2
No seal, applied pursuant to this metering code, shall be broken or removed except in the
presence of or with the prior consent of the agency affixing the seal or on whose behalf
the seal has been affixed unless it is necessary to do so in circumstances where (i) both
main and check meters are malfunctioning or there occurs a fire or similar hazard and
such removal is essential and such consent can not be obtained immediately (ii) such
action is required for the purpose of attending to the meter failure. In such
circumstances, verbal consent shall be given immediately and it must be confirmed in
writing forthwith.
21.3
Each party shall control the issue of its own seals and sealing pliers, and shall keep
proper register/record of all such pliers and the authorized persons to whom these are
issued.
21.4
Sealing of the metering system shall be carried out in such a manner so as not to hamper
downloading of the data from the meter using CMRI or a remote meter reading system.
22.
Assessment of consumption of defective and/or stuck-up meter
22.1
Whenever a meter goes defective, the consumption recorded by the check meter / backup
meter / secondary backup (i.e. receiving end meters) shall be referred. The details of the
malfunctioning along with date and time and snaps shot parameters along with load
survey shall be retrieved from the main meter. The exact nature of the mal-functioning
shall be brought out after analyzing the data so retrieved and the consumption / losses
recorded by the main meter shall be assessed accordingly. If main as well as back up
metering systems become defective, the assessment of energy consumption for the
outage period shall be done from the backup meters by the concerned parties as mutually
agreed or at the level of Metering Committee.
22.2
If main as well as check metering systems become defective, the assessment of energy
consumption for the outage period shall be done by the concerned parties as mutually
agreed or at the level of Metering Code Committee.
23.
Replacement of Defective or Stuck-up Meter
Defective or stuck-up meter shall be replaced as soon as possible. The owner of the
meter shall maintain spare inventory of meters in sufficient quantity, so that down time is
minimized.
24.
Interface Metering Arrangement
24.1
The metering system shall comprise of main, check, backup and secondary backup
meters. In the event of main meter becoming defective the order of precedence for billing
shall be (a) main (b) check (c) backup (d) secondary backup.
24.2
Generating Stations:
Metering Code for Assam Grid
Page 20
April 2004
24.2.1 Meters shall be installed on each Generator terminal, at each Unit Auxiliary
Transformer (UAT), and all outgoing feeders at Generating Stations to work out
energy generated and net energy delivered by the power station in the grid.
24.2.2 For measurement of energy supplied by major generating stations within the
state, meters shall be provided on each outgoing feeder at the power station
designated as main meter for billing purpose as per commercial agreement and/or
Grid Code Connectivity Conditions.
24.2.3 Meters shall also be provided on the other end of EHV feeders to serve as
secondary back-up meter. Meters on each generator and each auxiliary
transformer shall work as backup meters. The consumption recorded by main
meter shall be compared with the consumption recorded by secondary backup
meter on EHV feeder to work out transmission losses as well as to monitor the
correct functioning of both meters.
24.3
Interstate Transmission and Inter-Regional Transmission System:
24.3.1 Metering arrangement for Inter-State Transmission Lines and for Inter-Regional
Transmission System shall be governed by IEGC. Special Energy Meters (SEM)
capable of time-differentiated measurement (15 minutes) of active energy and
voltage differentiated measurement of reactive energy as specified by
CTU/NERLDC shall be provided on interstate and inter-regional transmission
lines. Assam Gridco shall comply with requirement for installation, meter reading
& downloading and communication of readings of Special Energy Meters (SEM)
to NERLDC as per operating procedure of NERLDC. Assam Gridco may install
its own Check Meters at inter-state/inter-regional transmission lines at the
periphery of Assam State Transmission System.
24.4
Special requirement
The above meters provided on interstate/inter-regional transmission lines, and on the lines
connected to major generating stations within the state shall have following facilities:
(a)
Metering equipment shall have external / internal modem so as to be capable of
remote transmission of all data available in the meter memory through any of the
information link viz. radio frequency, Public Switched Telephone Network
(PSTN), Power Line Carrier Communication (PLCC) lines, V-SAT Network,
Mobile and other means of telemetry like private network of Assam Gridco or low
power radio.
(b)
The metering equipment shall be of draw out type modular metering units with
facility of automatic CT short-circuiting. Meter mounting shall be projection type
or rack type as per space and site requirement.
(c)
The meters shall be capable of powered up with 230V, AC auxiliary supply and
110V or 220V DC supply of sub-station so that metering cores VT is never loaded.
The meter will normally be powered up by AC auxiliary supply and will be
switched over to DC supply only when AC auxiliary supply fails.
(d)
The meter shall be capable of data transmission to RTU’s as well Intelligent
Electronic Device (IED). The format / protocol of communication for data retrieval
and data telex should be made known to owner of meter by the concerned meter
supplier.
Metering Code for Assam Grid
Page 21
April 2004
24.5
Metering between Assam Gridco-Distribution Licensee:
(a) For measurement of power delivered by Assam Gridco to Distribution Licensee,
metering shall be provided on the LV side of EHV Power Transformer i.e. 33kV side
of 132/33kV and 33 kV side and 11 kV side of 132/33/11 kV and 11kV side of
132/11kV transformers installed in EHV sub-stations.
Operational meters shall also be provided on all outgoing 33kV and 11kV feeders as
back-up meter for energy audit on feeder and reconciliation of energy with respect to
energy measured on LV side of EHV Power Transformer.
(b) In case of EHV industrial and oil and mining, tea plantation and other consumers
directly fed from 220kV or 132kV sub-stations, tariff metering shall be provided on
outgoing feeder emanating from EHV sub-station.
24.6
Metering between two Distribution Licensee:
The energy metering shall be provided at such points of the power lines connecting any
two Distribution Systems owned by different Distribution Licensees so that the measured
energy gives correct measurement of consumption by either Distribution Licensee.
If installation of metering at such point is not feasible, it shall be provided at nearest substation feeding other Distribution System. In such case, energy accounting may be in
proportion to installed capacity of Distribution Transformers on the line or as agreed
mutually.
24.7
Sub-station Auxiliary Consumption Metering:
The Assam Gridco sub-stations auxiliary consumption shall be recorded on LV side of
station auxiliary transformers. If such transformer(s) is feeding other local load (colony
quarters, streetlights etc.) apart from sub-station auxiliary load, separate metering shall
be provided on individual feeders.
24.8
Open access User:
The direct open access consumers connected to NE regional transmission system shall
provide special Energy Meters. The embedded open access consumers within the intra
State Transmission System shall also provide special Energy Meters both at the point of
injunction and point of drawal of supply. Special Energy Meters (SEM) shall be capable
of time-differentiated measurement (15 minutes) of active energy and voltage
differentiated measurement of reactive energy as specified by CTU/NERLDC.
The Distribution licensee may provide Check Meters of the same specification as Main
Meters.
24.9
Operational Metering:
Operational metering shall be sited wherever reasonably required by Assam
Gridco/Generating Companies for applications other than tariff metering.
Metering Code for Assam Grid
Page 22
April 2004
25.
ABT, Two Part and ToD Tariff Capability
25.1
The ABT compliant meter will have provision to compute and store average active and
reactive energy and load data with respect to system frequency and the integration of the
data i.e. average kWh & kVarh, and average frequency for 15 minutes block will be
available in each meter.
25.2
Meters shall also have reactive high and reactive low volt-ampere hour registers for total
drawl, high & low system voltage drawl. The Distribution Licensee wise summation of
kWh, kW, PF, demand scheduled interchange/ unscheduled interchange will be done at
the main computer station provided at central billing station or at Load Despatch Centre.
25.3
The metering arrangement for recording Distribution Licensee consumption/power input
in his area of supply shall consist of following:
(a) Frequency based ABT compliant meters shall be provided on 220 kV / 132 kV lines
feeding each Distribution Licensee area of supply. The function of these meters will
be as under:
(1) To measure Distribution Licensee -wise schedule and unscheduled interchange of
energy.
(2) To monitor and measure Distribution Licensee-wise kW/kVAr, kVA demand,
hourly power factor and MVAr flow including MVAr exchange above 103% and
below 97% of rated system voltage.
For this purpose, the various parameters shall be integrated at one centrally located
station preferably at load despatch centre at Jaipur through computer and suitable
software.
(b)
Static tri-vector meters to be provided on LV secondary side of all EHV
transformers. The function/duty of this meter will be as under:
(1) Measurement of kWh energy supplied to Distribution Licensee for billing
purpose.
KW/kVA demand and power factor, hourly as well monthly caused by Discom on each
EHV transformer. The metering arrangement between Assam Gridco and Distribution
Licensee
26.
Metering Code Committee
26.1
Assam Gridco shall be responsible for managing and serving the Metering Code for
Assam Grid with each constituents/Users of intra State Transmission System discharging
respective obligations under the Code.
26.2
The Grid Code Review Committee shall establish a Metering Code Committee (MCC) in
accordance with Grid Code and such Committee shall consist of the following:
(a) A Chairman, who is an Officer designated by Assam Gridco.
(b) A Member (Secretary), who is also an Officer from Assam Gridco.
Metering Code for Assam Grid
Page 23
April 2004
(c) One representative from each of the Generating Companies
(d) One representative from each of the Distribution Licensees.
(e) One member from Power Grid Corporation of India (PGCIL) representing NERLDC.
(f) One Member from IPPs (functioning) connected to the state transmission system.
(g) One member representing Open Access Consumers for state transmission system.
26.3
The rules to be followed by the Committee in conducting their business shall be
formulated by the Committee themselves and shall be approved by Grid Code Review
Committee. The Committee shall meet at least once in six (6) months and conduct the
following functions:
(a) To keep Metering Code and its working under scrutiny and review.
(b) To consider all requests for amendment to the Metering Code which any user makes.
(c) To publish recommendations for changes to the Metering Code together with the
reason for the change and any objection if applicable.
(d) To issue guidance on the interpretation and implementation of the Metering Code.
27.
Mechanism for Dispute Resolution
Any disputes relating to inter-utility metering between Assam Gridco and any
Generating Company/Distribution Licensees/Users shall be settled in accordance with
procedures given in Assam Grid Code. The dispute relating to billing and settlement
among the entities shall be resolved under relevant agreements like Power Purchase
Agreements (PPA) etc.
28.
Dynamic Code
The Metering Code requires review and updation from time to time in view of
continuously and fast changing metering and communication technology and for new
commercial agreements and tariff, industry structure. All changes and revision in the
Metering Code shall be discussed in Metering Code Committee and approved by the
Commission.
Metering Code for Assam Grid
Page 24
April 2004
ANNEXURE-2A
MINIMUM ACCEPTABLE SPECIFICATIONS
CURRENT TRANSFORMERS (CT) FOR METERING
Sr. Particulars
No.
1. Nominal System
Voltage (kV rms)
2. Highest System
Voltage (kV rms)
3. Reference Standard
4. Standard CT Ratio
No. of Metering
cores
6. Rated Continuous
Thermal Current
7. Rated Short time
thermal primary
current for 1 second
8. CT characteristics:
(a) Rated Primary
Current (Amps)
11kV
33kV
132kV
220kV
11
33
132
220
12
36
145
245
2000-1000/1-1
1600-800/1-1
1200-600/1-1
800-400/1-1
600-300/1-1
400-200/1-1
300-150/1-1
150-75/1-1
IS 2705 with latest amendments
800-400/1-1
400/1-1
600-300/1-1
200/1-1
400-200/1-1
100/1-1
300-150/1-1
50/1-1
100-50/1-1
5.
(b) Rated Secondary
Current (Amps)
(c) Accuracy Class
(d) Maximum
Instrument Security
Factor (ISF)
(e) Rated Secondary
Burden (VA)
9. Reference Standard
for insulating oil
Metering Code for Assam Grid
800/1-1
Two
120% of Rated Primary Current
25
25
31.5
40
2000-1000
800-400
400
800
1600-800
1200-600
800-400
600-300
400-200
300-150
150-75
1 or 5
600-300
400-200
300-150
100-50
200
100
50
1 or 5
1 or 5
1 or 5
0.5
5
0.5
5
0.5
5
0.5
5
30
30
30
40
IS 335 with latest amendments
Page 25
April 2004
ANNEXURE-2B
MINIMUM ACCEPTABLE SPECIFICATIONS FOR
EHV CAPACITOR VOLTAGE TRANSFORMERS (CVT) FOR METERING
Sr.
No.
1.
2.
3.
4.
5.
Particulars
Nominal System Voltage (kV rms)
Highest System Voltage (kV rms)
Reference Standard
Rated Capacitance (pF)
For low voltage terminal over
entire carrier frequency
(a) Stray Capacitance
(b) Stray Conductance
6. (a) High frequency capacitance for
entire carrier frequency range
(b) Equivalent Series Resistance
over the entire frequency range
7. No. of Secondary Windings for
potential measurement devices
8. Standard Voltage Ratio
(a) Winding-I
(b) Winding-II
9. Rated Secondary Burden (VA)
(a) Winding-I
(b) Winding-II
10. Accuracy Class
(a) Winding-I
(b) Winding-II
11. Rated Voltage Factor and
Duration
(a) Winding-I
(b) Winding-II
12. Reference Standard for insulating
oil
Metering Code for Assam Grid
132kV
220kV
132
220
145
245
IS 3156 with latest amendments
4400 pF with tolerance +10% and -5%
Shall not exceed 200 pF
Shall not exceed 20 micro siemens
Within 80% to 150% of rated capacitance
Less than 40 ohms
Two
Two
132kV/√3 / 110V/√3
132kV/√3 / 110V/√3
220kV/√3 / 110V/√3
220kV/√3 / 110V/√3
50
50
50
50
0.5
0.5
1.2 continuous and 1.5 for 30 seconds
1.2 continuous and 1.5 for 30 seconds
IS 335 with latest amendments
Page 26
April 2004
ANNEXURE-2C
MINIMUM ACCEPTABLE SPECIFICATIONS OF
EHV POTENTIAL TRANSFORMERS FOR METERING
Sr.
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Particulars
Nominal System Voltage (kV rms)
Highest System Voltage (kV rms)
Reference Standard
No. of Secondary Windings for
potential measurement devices
Standard Voltage Ratio
(a) Winding-I
(b) Winding-II
Rated Secondary Burden (VA)
(a) Winding-I
(b) Winding-II
Accuracy Class
(a) Winding-I
(b) Winding-II
Rated Voltage Factor and
Duration
(a) Winding-I
(b) Winding-II
Reference Standard for insulating
oil
Metering Code for Assam Grid
132kV
220kV
132
220
145
245
IS 3156 with latest amendments
Two
Two
132kV/√3 / 110V/√3
132kV/√3 / 110V/√3
220kV/√3 / 110V/√3
220kV/√3 / 110V/√3
50
50
50
50
0.5
0.5
1.2 continuous and 1.5 for 30 seconds
1.2 continuous and 1.5 for 30 seconds
IS 335 with latest amendments
Page 27
April 2004
ANNEXURE-2D
MINIMUM ACCEPTABLE SPECIFICATIONS OF DEDICATED
HV POTENTIAL TRANSFORMERS (PT) FOR METERING
Sr.
No.
1.
2.
3.
4.
5.
6.
7.
8.
Particulars
33kV
Nominal System Voltage (kV rms)
Highest System Voltage (kV rms)
Reference Standard
No. of Secondary Windings for
potential measurement devices
Standard Voltage Ratio (for both
windings)
Rated Secondary Burden (VA) per
winding
Accuracy Class (At 10% to 100%
of rated VA burden)
Rated Voltage Factor and
Duration
33
11
36
12
IS 3156 with latest amendments
Two
Two
Metering Code for Assam Grid
11kV
33kV/√3 / 110V/√3
11kV/√3 / 110V/√3
50
50
0.5
0.5
1.2 continuous and 1.5 for 30 seconds
Page 28
April 2004
ANNEXURE-2E
MINIMUM ACCEPTABLE SPECIFICATIONS CT-PT SET FOR METERING
Sr. Particulars
No.
Specification of CT
1.
2.
3.
4.
Nominal System Voltage (kV rms)
Highest System Voltage (kV rms)
Reference Standard
Standard CT Ratio (Amps/Amps)
33kV
5.
6.
33
36
IS 2705 with latest amendments
200-100/1-1
100-50/1-1
120% of rated primary current
25
(b)
(c)
(d)
(e)
8.
200-100
100-50
1
0.5
<10
30
IS 335 with latest amendments
Rated continuous thermal current
Rated short time thermal primary current for 1 second
(in kA)
7. CT Characteristic:
(a) Rated Primary Current (Amps)
Rated Secondary Current (Amps)
Accuracy Class
Maximum Instrument Security Factor (ISF)
Rated Secondary Burden (VA)
Reference Standard for insulating oil
Specification of PT
1.
2.
3.
4.
5.
6.
7.
8.
Nominal System Voltage (kV rms)
33
Highest System Voltage (kV rms)
36
Reference Standard
IS 3156 with latest amendments
No. of Secondary Windings for potential measurement
Two
devices
Standard Voltage Ratio
33kV/√3 / 110V/√3
Rated Secondary Burden (VA) per winding
50
Accuracy Class (At 10% to 100% of rated VA burden)
0.5
Rated Voltage Factor and Duration
1.2 continuous and
1.5 for 30 seconds
Metering Code for Assam Grid
Page 29
April 2004