Download Data Dictionary for Electric System Security Data

873997698
Version 1.1 December 5, 2000
Data Dictionary for Electric System Security Data
Introduction
The data and terms described here are intended as a definition and clarification of the electric system
security data listed in Appendix 4B-A of NERC Policy 4B, System Coordination – Operational Security
Information. Each term is defined and its current or expected method of exchange is specified. A number
of additional security data types that would be useful to security coordinators and control areas are also
identified, although they have not been defined.
Issues and Limitations
1. Some systems are incapable of sending derived data, or using derived data from other systems.
2. It is assumed that Ampere measurements are used only for thermal limits calculations, and therefore,
only an absolute value is required.
3. In some cases, MVAR Gross Output is measured rather than MVAR Net Output. Either value is
usable provided the actual data type is known by the receiver.
4. There are a number of data types in existence today that did not exist when the original data types
were defined (e.g. retail items). These are not included in this data dictionary.
5. The only reference in NERC documentation to the direction that is to be assigned to negative and
positive flows is in the Area Interchange Error Survey Training Document. This document specifies
that net power into a control area is to be entered into the survey as a negative number, and net power
out of a control area is to be entered as a positive number; no other reference to sign and direction has
been found in NERC documents. This practice has not been adopted for normal operations by all
security coordinators and control areas. As no industry standard for direction exists, the following
convention is adopted for data transferred over the ISN: flow out of a metering point is positive, and
flow into a metering point is negative. Specific meanings for the power system elements lines,
generators, and loads are as follows:
 Flow out of a company over a tie line is positive.
 Flow out of a generating unit into a station is positive.
 Flow out of a load station is positive.
6. The ICCP standard does not discuss the scaling of analog quantities. In order to address this
deficiency, the ISN Data Point Definition – Analog and Status Value Format document specifies that
the source control area must define the ax + b scaling parameters required to convert the units and
sign of each data point into the units and direction as specified above. It is the responsibility of the
entity receiving the data to apply the scaling parameters to the data value received.
7. There is no standard way of determining exactly what is being measured. (i.e. there is no standard
naming convention across all control areas and security coordinators.)
Additional Data Types to be Considered
The data types that are currently listed in Appendix 4B-A of NERC Policy 4B are defined in the sections
below. This section lists additional data types that may be considered for exchange over NERCnet in the
future in order to support the following information requirements:
1. Real-time information so that security coordinators and control areas have the information they need
to assess the present state of the power system and to take appropriate actions to ensure its reliability.
2. Operational planning information so security coordinators can sufficiently assess expected operation
and can coordinate plans to maintain a reliable state. Security coordinators would want this data for
up to a week into the future; others may need to cover a longer period.
3. Other information. This is longer-term data similar to operational planning information and would
include items that change the bulk power system.
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As a minimum, the following additional data types are needed to support these information requirements:
1. MVar loading.
2. Instantaneous interchange total and limits for all lines contributing to a flow gate, not just by
individual line.
3. Current total interchange schedules with each control area.
4. All real-time operating security limits being used that are applicable to the bulk system and of interest
to other control areas and security coordinators, not just special limits.
5. Forecast of operating reserve at peak and time of peak for next 7 days (only current and next day
given below).
6. Forecast peak demand for next 7 days (only current and next day given below).
7. Modified equipment being returned to service, including description of its operating characteristics
(i.e. nameplate ratings, location of connection, etc). (Only new facilities given below.)
8. Modified special protection systems (only new special protection systems given below).
9. All types of security alerts.
Transmission Data
Status
Description
Status of the switching devices (breakers, switches, disconnects) at each end of a transmission line.
Possible values are Open, Closed, and Between. Derived status of lines, line segments, transformers,
capacitors, and reactors, subject to the derived status limitation noted above. Possible values are Inservice, Out-of-service, and Between. The meaning of In-service and Out-of service for lines and line
segments is as agreed between the parties exchanging this data.
Exchange Mechanism
ISN (ICCP)
MW Loading
Description
Instantaneous real power flow on the transmission line. Direction indicated by positive and negative
values is determined by the location of the metering point. Flow is positive out of a metering point into
the line.
Exchange Mechanism
ISN (ICCP)
Ampere Loading
Description
Instantaneous current flow at a defined location on the transmission line
Exchange Mechanism
ISN (ICCP)
MVA Capability
Description
MVA limit for transmission devices. This may be either a static or dynamic limit.
Exchange Mechanism
ISN (ICCP)
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Transformer Tap Setting
Description
Predefined, fixed positions on one or both sides of a transformer. Each Tap position represents a specific
voltage value, (i.e. changing a Tap Position changes the voltage.) There is no standard numbering scheme
for the tap position. For example, some utilities number beginning at 0, others at 1. Other utilities refer
to the nominal position as position 0, with positive integers for positions above nominal, and negative
integers for positions below nominal. Still other utilities use turns ratio and not position notations.
Exchange Mechanism
ISN (ICCP)
Transformer Phase Angle Setting
Description
Represents the Phase Angle between the current and voltage. (i.e. changing the Phase Angle changes the
power.) The angle settings can typically vary between -90 and +90. The unit of measurement is Degrees.
Exchange Mechanism
ISN (ICCP)
Key Voltage
Description
Instantaneous voltage measurement at a defined location on the transmission network. Unit of
measurement is kV. PerUnit, 100Base, 120Base, etc. voltages must be converted to simple kV readings
by the receiver.
Exchange Mechanism
ISN (ICCP)
Generator Data
Status
Description
Status of the generator as telemetered, or as derived from the status of the breaker associated with the
generator unit. Possible values are In-service, Out-of-service and Between, or On, Off and Between.
Some utilities have additional statuses such as Dispatchable, On AGC, Off AGC, and Unavailable. These
additional statuses require the use of the ICCP Discrete Point Type. Since no standard exists for using
this data type for status information, the meanings of the values are determined by agreement between the
parties exchanging the information.
Exchange Mechanism
ISN (ICCP)
MW Capability
Description
Limit on the gross or net MW output of a generator unit. This value may be either a static or dynamic
limit. The direction indicated by positive is out of the generator into the station.
Exchange Mechanism
ISN (ICCP)
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MVAR Capability
Description
High or low limit on the gross or net MVAR output of a generator unit at the current MW output. This
value may be either a static or dynamic limit. The direction indicated by positive is out of the generator
into the station.
Exchange Mechanism
ISN (ICCP)
MW Net Output
Description
Instantaneous measurement of the net real output power from the generator. The direction indicated by
positive is out of the generator into the station.
Exchange Mechanism
ISN (ICCP)
MVAR Net Output
Description
Instantaneous measurement of the net imaginary output power from the generator. The direction
indicated by positive is out of the generator into the station.
Exchange Mechanism
ISN (ICCP)
Status of Automatic Voltage Control Facilities
Description
Instantaneous status of automatic voltage regulators, and if they exist, the statuses of fast acting exciters
and stabilizers. Possible values are In-service, Out-of-service, and Between, or On, Off, and Between.
Exchange Mechanism
ISN (ICCP)
Operating Reserve
MW Reserve Available Within Ten Minutes
Description
The amount of additional power that can be made available to the system within 10 minutes, as defined in
Policy 1 of the NERC Operating Manual.
Exchange Mechanism
ISN (ICCP)
Control Area Demand
Instantaneous Control Area Demand
Description
Instantaneous reading of the primary demand for the control area. The unit of measurement is MW.
Exchange Mechanism
ISN (ICCP)
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Interchange
Instantaneous Actual Interchange With Each Control Area
Description
Instantaneous reading of the MW flow between control areas. Direction indicated by positive is out of the
source control area.
Exchange Mechanism
ISN (ICCP)
Current Interchange Schedules With Each Control Area By Individual Interchange
Transaction
Description
Current scheduled MW flows between control areas, and may include interchange identifiers and reserve
responsibilities.
Exchange Mechanism
E-Tagging and IDC.
Interchange Schedules For the Next 24 Hours
Description
Interchange schedules with each control area by individual interchange transaction for the period
encompassing the next hour to 24 hours into the future.
Exchange Mechanism
E-Tagging and IDC.
Area Control Error and Frequency
Instantaneous Area Control Error
Description
Instantaneous measurement of the area control error. Unit of measurement is MW. Value may be
positive or negative.
Exchange Mechanism
ISN (ICCP)
Clock Hour Area Control Error
Description
Instantaneous Area Control Error averaged since the start of the current hour. This value may be positive
or negative. Unit of measurement is MW.
Exchange Mechanism
ISN (ICCP) (future)
System Frequency At One or More Locations in the Control Area
Description
Instantaneous reading of the actual frequency in Hz. This is not the deviation from a value (nominally 60
Hz).
Exchange Mechanism
ISN (ICCP)
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Other Operating Information
Special Operating Security Limits in Effect
Description
Notification of special operating security limits in effect.
Exchange Mechanism
SCIS in the past. Slowly migrating from SCIS to SDX.
Forecast of Operating Reserve at Peak, and Time of Peak for Current Day and
Next Day
Description
Estimate of the operating reserve at the time of peak demand. Unit of measurement is MW. The time is
the local clock time, with time zone specified, for the peak demand.
Exchange Mechanism
SDX
Forecast Peak Demand for Current Day and Next Day
Description
Estimate of the peak demand for the day. Unit of measurement is MW.
Exchange Mechanism
SDX, SCIS
Forecast Changes in Equipment Status
Description
Notification of expected changes in availability of equipment, or special protection schemes, such as
equipment being placed into service or taken out of service for periods of time exceeding one hour
(negotiable), such as for maintenance.
Exchange Mechanism
SDX, SCIS
New Facilities in Place
Description
Notification of new equipment being placed into service
Exchange Mechanism
SCIS, SDX
New or Degraded Special Protection Systems
Description
Notification of changes to the status of special protection schemes and systems.
Exchange Mechanism
SCIS, SDX
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Emergency Operating Procedures in Effect
Description
Notification of Emergency conditions and procedures and expected duration. This may also include
Transmission Loading Relief states, Capacity Deficiency Alerts, and relevant information such as action
taken or planned.
Exchange Mechanism
SDX, SCIS, IDC
Severe Weather, Fire, or Earthquake
Description
Notification of severe weather conditions such as hurricanes, tornadoes, and severe thunderstorms. May
also include tornado and severe weather warnings and watches, and solar magnetic disturbance alerts.
Also includes notification of earthquakes, and fires that affect or could potentially affect the power system
operation.
Exchange Mechanism
SDX, SCIS
Multi-site Sabotage
Description
Notification of cases of sabotage to power system equipment at multiple sites.
Exchange Mechanism
SDX, SCIS
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