Download Draft Information Document Generating Unit Technical Requirements ID# 2011-012R

Draft Information Document
Generating Unit Technical Requirements
ID# 2011-012R
Information documents are for information purposes only and are intended to provide guidance. In the
event of any discrepancy between the information document and the related authoritative document(s) in
effect, the authoritative document(s) governs. Please submit any questions or comments regarding this
information document to [email protected].
1
Purpose and Background
This information document supports section 502.5 of the ISO rules, Generating Unit Technical
Requirements and provides additional guidance which may be of interest to legal owners of synchronous
generating units in Alberta.
This guidance, as well as any examples provided hereinin this information document, are not meant to be
authoritative, and do not introduce any additional requirements for market participants; they. They are
intended only as information.
To assist users, the AESO has cross-referenced each subsection in this information document with the
corresponding subsection in section 502.5.
2
Related Authoritative Documents
The AESO’s authoritative documents consist of ISO rules, the ISO tariff and the Alberta reliability
standards. Authoritative documents contain binding rights, requirements and obligations for market
participants and the AESO. Market participants and the AESO are required to comply with provisions set
out in its authoritative documents.
Market participants are encouraged to review the following related authoritative documents:
Section 502.5 of the ISO rules, Generating Unit Technical Requirements
Section 502.5 sets out the minimum technical requirements for a new synchronous generating unit
connecting to the transmission system, one already connected and in existence, and one already
connected and in existence which is undergoing a material change to any components comprising the
generating unit
Section 502.6 of the ISO rules, Generating Unit Operational Requirements
Section 502.6 sets out operating requirements for a legal owner of a generating unit to operate the
generating unit as it is designed to operate.
Section 304.4 of the ISO rules, Maintaining Network Voltage
Section 304.4 sets out voltage adjustment requirements for generating units.
Alberta Reliability Standard VAR-001-AB-1a Voltage and Reactive Control
VAR-001-AB-1a sets out requirements such that transmission voltage levels, reactive power flows, and
reactive power resources are monitored, controlled and maintained within limits in real-time to protect
equipment and the reliable operation of the Interconnection.
Alberta Reliability Standard VAR-002-AB-1.1b Generator Operation for Maintaining Network Voltages
VAR-002-AB-1.1b sets out requirements to ensure generating units and aggregated generating facilities
provide reactive power and voltage control necessary to ensure voltage levels, reactive power flows and
reactive power resources are maintained within applicable facility ratings to protect equipment and the
reliable operation of the Interconnection.
Alberta Reliability Standard VAR-002-WECC-AB-1 Automatic Voltage Regulators and Voltage Regulating
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Systems
VAR-002-WECC-AB-1 sets out requirements to ensure that automatic voltage regulators on generating
units and synchronous condensers are in service and controlling voltage; and voltage regulating systems
at aggregated generating facilities are in service and controlling voltage.
Alberta Reliability Standard VAR-501-WECC-AB-1 Power System Stabilizer
VAR-501-WECC-AB-1 sets out requirements to ensure that power system stabilizers on generating units
are kept in service.
AESO Protection Standard
The AESO Protection StandardSection 502.3 of the ISO rules, Interconnected Electric System Protection
Requirements
Section 502.3 sets out the minimum level of protection for facilities connecting to the transmission system
prior to the effective date of section 502.5.
23 Functional Specification (Corresponds to section 502.5, subsection 2)
Section 502.5 sets out the expectations regarding functional specifications. The AESO recognizes that
legal owners that connected a generating unit to the transmission several years ago may not have
received a functional specification. In these cases, as described in section 502.6, the AESO will work
with the legal owner and create a functional document setting out the important operational parameters
associated with that generating unit such that the legal owner and the AESO are clear and aligned on the
operating capabilities of the generating unit. Please refer to section 502.6 and AESO Information
Document 2012-023R for additional information.
34 Maximum Authorized Real Power (Corresponds to section 502.5, subsection 4)
This example is intended to provide guidance on how maximum authorized real power is determined.
(a) maximum authorized real power = 100.0 MW;
(b) lagging reactive power obligation (0.90 power factor) = 48.4 MVAr;
(c) leading reactive power obligation (0.95 power factor) = 32.9 MVAr; and
(d) MVA rating at this value = 111.1 MVA.
In many cases the maximum authorized real power will not be the same as the nameplate rating.
Examples include:
(a) A generating unit with a nameplate of 100 MVA at 0.85 power factor that has a rated output of 85
MW. Section 502.5 only requires the generating unit to operate up to 0.90 power factor which
could result in this same generating unit being able operate at 90 MW and still meet the
requirements of section 502.5.
(b) A generating unit equipped with a gas turbine and a nameplate of 100 MVA at 0.90 power factor
that has a rated output of 90 MW. The nameplate rating of gas turbines are for specific
temperatures and pressures; in. In Alberta, the colder temperatures allow gas turbines to operate
at values significantly above the nameplate values. Depending on the generating unit cooling
and automatic voltage regulator supplied with the generating unit, the outputgenerating unit may
be able to achieve an output over 110 MW and still be in compliance with the requirements of
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section 502.5.
(c) There are other factors which could result in the maximum authorized real power not being the
same as the nameplate rating, including the capability of the turbine, shaft or coupling ratings,
etc. An example would be a generating unit that has a turbine capable of producing 200 MW
andwhich is coupled to a generator that is also capable of 200 MW at 0.90 power factor. The
coupling may only have a rating of 190 MW; in this case, this would be the maximum authorized
real power for this generating unit.
Section 502.5 requires a legal owner to consider the under and over-excitation limiter settings when
determining the maximum authorized real power. If the limiters cause the reactive power capability of the
generating unit to be reduced such that the 0.90 or 0.95 power factor requirements cannot be met, then
the maximum authorized real power will be reduced accordingly. As part of the AESO’s connection
process, the legal owner may apply to the AESO to mitigate this through the use of external dynamic
reactive power resources such as static VAr compensators, synchronous condensers, etc., which the
AESO will document in the functional specification for the generating unit
45 Voltage Ride-Through for Existing Generating Units (Corresponds to Section 502.5, subsection 6)
When determining the voltage ride-through capability for an existing generating unit, the legal owner
should consider the voltage level at the point of connection which would be used as the 100% voltage for
the voltage ride-through requirements. In Alberta, voltages may vary considerably from the nominal
voltage. For example the voltages at Anderson substation area are listed in Table 1 below:
Table 1 - Anderson Substation Voltage
Substation Name
and Number
Nominal
Voltage
(kV)
Anderson A801S
Minimum
Operating Limit
(kV)
Desired
Maximum
Range
Operating Limit
(kV)
(kV)
240
255
257 - 268
275
144
145
146 - 152
155
As illustrated in Table 1 for both the nominal 144 kV and 240 kV levels, the minimum operating limit is
above the nominal voltage value and the desired range can exceed ten percent (10%%) above the
nominal voltage value. The AESO plans the transmission system to operate at voltage levels of +/-plus or
minus five percent (+/- 5%%) for N-0 (normal system) and plus or minus 10%ten percent (+/- 10%) for N1 contingencies. Based on the AESO’s operating practices, it is necessary for the AESO to ensure that
the generating units will remain on-lineonline during N-1 contingencies. The length of time that the
transmission system operates at the higher limits is dependent on the nature of the contingency and as
such, the generating units are required to operate continuously at the limits.
A generator trip is when the generating unit breaker or the transmission system breaker that supply the
generating unit open based on a trip signal from the generating unit protection. This protection may be
electrical, mechanical or process based. The AESO suggests that the legal owner of the facility consider
the following factors when determining the voltage ride -through capability:
(a) protection functions pick-up, time out and results in the generatorgenerating unit or critical
device(s) tripping;
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(b) contactors drop out, causing a critical device to go off- line;
(c) critical motors stallstalling; and
(d) other conditions that will result in the generating unit going off-line as a direct result of the voltage
disturbance.
In addition, the legal owner should consider the same factors for the post -transient voltage deviations as
defined withset out in section 502.5.
In appendix 1 of section 502.5, the solid line defines the transmission system voltages for which the
generating unit must ride-through and the shaded area defines the time frame that the generating units
and auxiliary systems must stay on-line for.
Section 502.5 refers to normal clearing times. However, the specific clearing times are not set out in
section 502.5 because they are set out in the AESO’s Protection Standard.Transmission Reliability
Criteria, Part II System Planning.
In some cases, the normal fault clearing times are greater or less than the typical values shown in the
AESO’s Protection Standard.section 502.3. In these cases, if the clearing time is:
(a) greater than nine (9) cycles, as section 502.5 specifies 49four (4) to nine (9) cycles, use nine (9)
cycles for the study; or
(b) less than four (4) cycles, as section 502.5 specifies 4to four (4) to nine (9) cycles, use four (4)
cycles for the study.
If the legal owner of the generating unit is unsure of the values to be useduse, the AESO suggests that
the legal owner contact the legal owner of the transmission facility to which the generating unit is
connected.
56 Voltage Ride-Through for New Generating Units (Corresponds to section 502.5, subsection 7)
Section 502.5, subsection 7 sets out voltage ride-through requirements for new generating units. The
concepts of how the voltage ride-through is determined is similar to the approach described above for
existing generating units. .
67 Voltage Regulation (Corresponds to section 502.5, subsection 8)
The AESO uses the term “point of control” in regards to the automatic voltage regulators to describe the
electrical point controlled by the automatic voltage regulator. Generally, this is the same point as the
voltage input to automatic voltage regulator which is typically the stator winding terminals of the
generating unit. Automatic voltage regulators commonly have control features that allow the point of
control to be moved away from voltage input to the automatic voltage regulator. This control feature is
commonly referred to as reactive current compensation or, in some cases, voltage droop.
Figures 2 through 4 provide examples onof various points of control to provide additional guidance.
Figure 2 Point of Control, Simplified Impedance Diagram Of a Single Generating Unit
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Point of Control range the AESO may
consider as per section 502.5
Stator Winding
Terminals
Point of Control as per
section 502.5
Transmission
System
Transmission
System Step-up
Transformer
Automatic Voltage
Regulator
Figure 3 - Point of Control, Simplified Impedance Diagram Of Multiple Generating Units on a
Common Bus
Automatic
Voltage
Regulator
Automatic
Voltage
Regulator
Stator Winding
Terminals
Common
bus
Automatic
Voltage
Regulator
Transmission
System
Transmission
System Step-up
Transformer
Point of Control as per
section 502.5
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Figure 4 - Point of Control, Simplified Impedance Diagram Of Multiple Generating Units with a
Single Measurement Point
Transmission
System Step-up
Transformer
Automatic
Voltage
Regulator
Stator Winding
Terminals
Automatic
Voltage
Regulator
Transmission
System
Point of Control range the
AESO may consider as per
section 502.5
78 Frequency and Speed Governing Requirements (Corresponds to section 502.5, subsection 9)
Section 502.5 states that a generating unit is required to have a governor system with droop control. This
requirement is in place to assist the AESO in maintaining sixty (60) Hz nominal frequency during:
(a) normal system operation that includes fluctuation in load;
(b) system disturbances; and
(c) islanded operation of a generating unit from the larger transmission system along with some load
external to the generating facility. Such an island may include other generating units.
During any of the above mentioned conditions, the generating unit may (but is not required to in
accordance with the section 502.5) trip off-line if the frequency goes outside of the boundaries illustrated
in Appendix 3 of section 502.5.
As additional guidance on how droop control works, the AESO offers the following guidance.:
(a) Generating units that are base loaded, (i.e. operating at full load) are not expected to respond to
low frequency excursions but with the governors free to react these generating units, would
respond to high frequency excursions. This includes the steam turbine generators portion of a
combined cycle or co-generation facilities.
(b) During islanded operation, the operator of a generating unit does not have visibility of the
transmission system or the actions of other generating units, therefore adjustments to the
generating unit frequency should be coordinated through the AESO system controller.
89 Power System Stabilizer (Corresponds to section 502.5, subsection 10)
Section 502.5 setsets out the conditions which require the legal owner of a generating unit to install a
power system stabilizer. For additional information on how power system stabilizers work please refer to:
Criteria to Determine Excitation System Suitability for PSS in WSCC System:
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http://www.wecc.biz/library/WECC%20Documents/Documents%20for%20Generators/Power%20System
%20Stabilizers%20Criteria%20to%20Determine%20Excitation%20System%20Suitability.pdf
WECC Power System Stabilizer Design and Performance Criteria:
http://www.wecc.biz/library/WECC%20Documents/Documents%20for%20Generators/Power%20System
%20Stabilizer%20Design%20and%20Performance%20Criteria.pdf
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910 Transmission System Step-Up Transformer (Corresponds to section 502.5, subsection 11)
For additional guidance on transformer sizing, the AESO offers the following guidance:
(a) In order to meet the requirements of subsection 11 of the section 502.5, the thermal capability of
the transformer must be equal to the apparent power of the generating unit (the vector addition of
the maximum authorized real power and the reactive power obligation) minus any loads that may
be tapped -off between the stator winding terminals and the transmission system step-up
transformer. Figure 5 illustrates this concept.
(b) The thermal capability is not necessarily the nameplate rating of the transformer. The legal
owner may use a higher apparent power capability than the nameplate rating of the transformer.
This higher apparent power capability would be acceptable as a variance if submitted with a
report that is stamped by an Alberta accredited engineer that documents the basis for the higher
capability.
Figure 5 -Transmission System Step-Up Transformer Sizing Example
Maximum authorized
real power = 100 MW
Lagging reactive
power requirements
(0.90 power factor) =
48.4 MVAr
Acceptable minimum transformer ratings
ONAN = 100MVA
ONAN/ONAF = 75/100 MVA
ONAN/ONAF/OFAF = 60/80/100 MVA
Apparent power =
111.1 MVA
Stator
Winding
Terminals
100.0 MVA
111.1 MVA
1.0 MVA
10.1 MVA
Power Potential
Transformer
Unit Service
Transformer
Excitation
System
Auxiliary
Systems
Transmission
System Step-up
Transformer
In this example all loads are
assumed to be 0.90 power
factor
11 Auxiliary Systems (Corresponds to section 502.5, subsection 12)
The AESO offers the following guidance on auxiliary systems:
(a) As pertaining to generating stations, IEEE defines auxiliary as “any item not directly a part of a
specified component or system but required for its functional operation”.
(b) The Electric Utilities Act defines a generating unit as:
“the component of a power plant that produces, from any source, electric energy and ancillary
services, and includes a share of the following associated facilities that are necessary for the
safe, reliable and economic operation of the generating unit, which may be used in common with
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other generating units:
(i) fuel and fuel handling equipment;
(ii) cooling water facilities;
(iii) switch yards;
(iv) other items.”.
Based on both of the above definitions, it is the AESO’s opinion that the legal owner should consider all
components supplying and within the facility that are crucial to the normal operation of the facility as part
of the auxiliary systems.
11
Synchrophasor Measurement System (Corresponds to section 502.5, subsection 18)
Section 502.5 makes reference to other ISO rules that may contain requirements regarding
synchrophasor measurement devices. The AESO encourages market participants to review section
502.9 of the ISO rules, Phasor Measurement Unit Technical Requirements which sets out requirements
for a legal owner implementing synchrophasor measurement device.
The AESO offers the following guidance on the requirements regarding the installation of a
synchrophasor measurement device when replacing protections systems:
(a) Most modern generating units are installed with multi-functions relays. Replacement of one of
these relays on a planned basis triggers the requirement for a synchrophasor measurement
device. It is the AESO’s opinion that most modern multi-function protection relays have
synchrophasor measurement capabilities which meet the requirements of section 502.5.
(b) For older generating units with protection systems comprised of single element relays, it is the
AESO’s opinion that unless the legal owner is replacing a single element due to failure (an
unplanned replacement) then the legal owner would generally install a multi-function relay. Such
a change triggers the requirement for a synchrophasor measurement device. The AESO also
notes that many modern single element relays also have synchrophasor measurement capability.
Revision History
Effective Date
Description of Changes
Yyyy-mm-dd
yyyy-mm-dd
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