PRC-019-2: Coordination of Generating Unit or Plant Capabilities, Voltage Regulating Controls, and Protection
To verify coordination of generating unit Facility or synchronous condenser voltage regulating controls, limit functions, equipment capabilities and Protection System settings.
4.1. Functional Entities
4.1.1 Generator Owner
4.1.2 Transmission Owner that owns synchronous condenser(s)
For the purpose of this standard, the term, “applicable Facility” shall mean any one of the following:
4.2.1 Individual generating unit greater than 20 MVA (gross nameplate rating) directly connected to the Bulk Electric System.
4.2.2 Individual synchronous condenser greater than 20 MVA (gross nameplate rating) directly connected to the Bulk Electric System
4.2.3 Generating plant/ Facility consisting of one or more units that are connected to the Bulk Electric System at a common bus with total generation greater than 75 MVA (gross aggregate nameplate rating).
18.104.22.168 This includes individual generating units of the dispersed power producing resources identified through Inclusion I4 of the Bulk Electric System definition where voltage regulating control for the facility is performed solely at the individual generating unit of the dispersed power producing resources.
4.2.4 Any generator, regardless of size, that is a blackstart unit material to and designated as part of a Transmission Operator’s restoration plan.
See the Implementation Plan for PRC-019-2.
R1. At a maximum of every five calendar years, each Generator Owner and Transmission Owner with applicable Facilities shall coordinate the voltage regulating system controls, (including in-service1 limiters and protection functions) with the applicable equipment capabilities and settings of the applicable Protection System devices and functions. [Violation Risk Factor: Medium] [Time Horizon: Long-term Planning]
1.1. Assuming the normal automatic voltage regulator control loop and steady-state system operating conditions, verify the following coordination items for each applicable Facility:
1.1.1. The in-service limiters are set to operate before the Protection System of the applicable Facility in order to avoid disconnecting the generator unnecessarily.
1.1.2. The applicable in-service Protection System devices are set to operate to isolate or de-energize equipment in order to limit the extent of damage when operating conditions exceed equipment capabilities or stability limits.
R2. Within 90 calendar days following the identification or implementation of systems, equipment or setting changes that will affect the coordination described in Requirement R1, each Generator Owner and Transmission Owner with applicable Facilities shall perform the coordination as described in Requirement R1. These possible systems, equipment or settings changes include, but are not limited to the following [Violation Risk Factor: Medium] [Time Horizon: Long-term Planning]:
- Voltage regulating settings or equipment changes;
- Protection System settings or component changes;
- Generating or synchronous condenser equipment capability changes; or
- Generator or synchronous condenser step-up transformer changes.
M1. Each Generator Owner and Transmission Owner with applicable Facilities will have evidence (such as examples provided in PRC-019 Section G) that it coordinated the voltage regulating system controls, including in-service2 limiters and protection functions, with the applicable equipment capabilities and settings of the applicable Protection System devices and functions as specified in Requirement R1. This evidence should include dated documentation that demonstrates the coordination was performed.
M2. Each Generator Owner and Transmission Owner with applicable Facilities will have evidence of the coordination required by the events listed in Requirement R2. This evidence should include dated documentation that demonstrates the specified intervals in Requirement R2 have been met.
1. Compliance Monitoring Process
1.1. Compliance Enforcement Authority
The Regional Entity shall serve as the Compliance enforcement authority unless the applicable entity is owned, operated, or controlled by the Regional Entity. In such cases the ERO or a Regional entity approved by FERC or other applicable governmental authority shall serve as the CEA.
1.2. Evidence Retention
The following evidence retention periods identify a period of time an entity is required to retain specific evidence to demonstrate compliance. For instances where the evidence retention specified below is shorter than the time since the last compliance audit, the Compliance Enforcement Authority may ask an entity to provide other evidence to show that it was compliant for the full time period since the last audit.
The Generator Owner and Transmission Owner shall retain evidence of compliance with Requirements R1 and R2, Measures M1 and M2 for six years.
If a Generator Owner or Transmission Owner is found non-compliant, the entity shall keep information related to the non-compliance until mitigation is complete and approved or for the time period specified above, whichever is longer.
The Compliance Enforcement Authority shall keep the last periodic audit report and all requested and submitted subsequent audit records.
1.3. Compliance Monitoring and Assessment Processes
- Compliance Audit
- Spot Checking
- Compliance Investigation
1.4. Additional Compliance Information
Examples of Coordination
The evidence of coordination associated with Requirement R1 may be in the form of:
- P-Q Diagram (Example in Attachment 1), or
- R-X Diagram (Example in Attachment 2), or
- Inverse Time Diagram (Example in Attachment 3) or,
- Equivalent tables or other evidence
This evidence should include the equipment capabilities and the operating region for the limiters and protection functions
Equipment limits, types of limiters and protection functions which could be coordinated include (but are not limited to):
- Field over-excitation limiter and associated protection functions.
- Inverter over current limit and associated protection functions.
- Field under-excitation limiter and associated protection functions.
- Generator or synchronous condenser reactive capabilities.
- Volts per hertz limiter and associated protection functions.
- Stator over-voltage protection system settings. ? Generator and transformer volts per hertz capability.
- Time vs. field current or time vs. stator current.
NOTE: This listing is for reference only. This standard does not require the installation or activation of any of the above limiter or protection functions.
For this example, the Steady State Stability Limit (SSSL) is the limit to synchronous stability in the under-excited region with fixed field current.
On a P-Q diagram using Xd as the direct axis saturated synchronous reactance of the generator, Xs as the equivalent reactance between the generator terminals and the “infinite bus” including the reactance of the generator step-up transformer and Vg as the generator terminal voltage (all values in per-unit), the SSSL can be calculated as an arc with the center on the Q axis with the magnitude of the center and radius described by the following equations
C = V2g /2 * (1/Xs -1/Xd)
R =V2g /2*(1/Xs +1/Xd)
On an R-X diagram using Xd as the direct axis saturated synchronous reactance of the generator, and Xs as the equivalent reactance between the generator terminals and the “infinite bus” including the reactance of the generator step-up transformer the SSSL is an arc with the center on the X axis with the center and radius described by the following equations:
C = (Xd-Xs )/2
R = (Xd+Xs )/2
Section G Attachment 1 – Example of Capabilities, Limiters and Protection on a P-Q Diagram at nominal voltage and frequency
Section G Attachment 2 – Example of Capabilities, Limiters, and Protection on an R-X Diagram at nominal voltage and frequency
Section G Attachment 3 – Example of Capabilities, Limiters, and Protection on an Inverse Time Characteristic Plot
During development of this standard, text boxes were embedded within the standard to explain the rationale for various parts of the standard. Upon BOT approval, the text from the rationale text boxes was moved to this section.
Rationale for Facilities section 22.214.171.124
For those dispersed power producing facilities that only perform voltage regulating control at the individual generating unit level, the SDT believes that coordination should take place at the individual generating unit level of the dispersed power producing resource. These facilities need to consider the Protection Systems at the individual units and their compatibility with the reactive and voltage limitations of the units. Where voltage regulating control is done at an aggregate level, applicability is already included under Facilities section 4.2.3.