Power Plant and Transmission System Protection Coordination Phase - PowerPoint PPT Presentation

Power Plant and Transmission System Protection Coordination Phase Distance (21) and Voltage-Controlled or Voltage-Restrained Overcurrent Protection (51V) NERC Protection Coordination Webinar Series June 16, 2010 Phil Tatro Jon Gardell

Disclaimer 2  The information from this webcast is provided for informational purposes only. An entity's adherence to the examples contained within this presentation does not constitute compliance with the NERC Compliance Monitoring and Enforcement Program ("CMEP") requirements, NERC Reliability Standards, or any other NERC rules. While the information included in this material may provide some of the methodology that NERC may use to assess compliance with the requirements of certain Reliability Standards, this material should not be treated as a substitute for the Reliability Standard or viewed as additional Reliability Standard requirements. In all cases, the entity should rely on the language contained in the Reliability Standard itself, and not on the language contained in this presentation, to determine compliance with the NERC Reliability Standards.

Agenda 3  Technical Reference Document Overview • Proposed Modifications  Objectives  Description of Protection Functions  Discuss and Describe System Events that Could Create Conditions that Would Cause Operation of These Functions  Detailed Coordination Information • Function 21 – Phase Distance Protection • Function 51V – Voltage-Controlled or Voltage-Restrained Overcurrent Protection

Agenda 4  What is Important to Coordination • Settings that Protect the Generator • Back Up for Transmission System Protection • Calculation of Apparent Impedance with Infeed Current • Generator Field Forcing Effects During System Stressed Voltage Conditions • Loadability Issues During Stressed System Conditions  Question and Answer

Technical Reference Document Overview 5  Introduction and Background – Blackout Recommendation TR-22 • SPCS’s Assignment  The Need for this Technical Reference Document - History and Background: • August 14, 2003 Blackout • Subsequent Events

Technical Reference Document Overview 6  Support of PRC Standards  Benefits of Coordination: • To the Generator Owner • To the Transmission Owner • To the Planning Coordinator  Reliability of the Bulk Electric System and Power Delivery to the Customer

Proposed Modifications to the Technical Reference Document 7  SPCS has received feedback on the document that requires revisions to Section 3.1 and Appendix E • The level of field forcing represented in the existing document is not as severe as intended • The document is being revised based on observed generator loading during system disturbances and computer modeling • Two methods are under development for assessing loadability of phase distance protection  SPCS will be seeking Planning Committee approval of revisions to the Technical Reference Document

Proposed Modifications to the Technical Reference Document 8  The substantive revisions are included in this Webinar session • Section 3.1 and Appendix E  Phase distance discussion and examples will be modified to provide more comprehensive guidance on generator relay loadability • Section 3.10  Voltage-restrained overcurrent examples have been revised  Other modifications: • Achieve common usage of terms • Remove discrepancies between and among Tables 2 and 3 and the excerpts from these tables • Correct some figures • Correct formatting problems

Objective 9  Increase knowledge of recommended generator protection for system back-up using phase distance and voltage-controlled or voltage-restrained overcurrent functions.  Facilitate improved coordination between power plant and transmission system protection for these specific protection functions.

Scope 10 10  Focus is on the reliability of the Bulk Electric System.  This Technical Reference Document is applicable to all generators, but concentrates on synchronous generators connected at 100-kV and above.  Distributed Generation (DG) facilities connected to distribution systems are outside the scope of this document.

The Need for Phase Distance System Back-Up Protection – Function 21 11 11  “The distance relay applied for this function is intended to isolate the generator from the power system for a fault which is not cleared by the transmission line breakers.”  “Within its operating zone, the tripping time for this relay must coordinate with the longest time delay for the phase distance relays on the transmission lines connected to the generating substation bus.” IEEE C37.102-2006 – Guide for AC Generator Protection, Section 4.6.1.1

The Need for Voltage-Controlled or -Restrained Overcurrent Protection – Function 51V 12 12  “Its function is to provide backup protection for system faults when the power system to which the generator is connected is protected by time-current coordinated protections.”  “The type of overcurrent device generally used for system phase fault backup protection is either a voltage- restrained or voltage-controlled time-overcurrent relay. Both types of relays are designed to restrain operation under emergency overload conditions and still provide adequate sensitivity for the detection of faults.” IEEE C37.102-2006 – Guide for AC Generator Protection, Section 4.6.1.2

Relay One-Line Showing All Generator Protection and Identifying Function 21 and 51V 13 13 87U 87T 51T 87G 50BF R 24 27 59 81 51TG 59GN/ 27TH 51V 21 21 32 40 46 51V 78 50/27

System Events that Could Cause Undesired Operation of These Protection Functions 14 14  System Fault Conditions • Miscoordination with system protection during a system fault  Non-Fault Stressed System Conditions • System Low Voltage Conditions – Loadability Concerns • Events such as August 14, 2003 Blackout with embedded stressed system conditions  Loss of Critical Units

General Data Exchange Requirements – Generator Owner Data and Information 15 15  The following general information must be exchanged in addition to relay settings to facilitate coordination, where applicable: • Relay scheme descriptions • Generator off nominal frequency operating limits • CT and VT/CCVT configurations • Main transformer connection configuration • Main transformer tap position(s) and impedance (positive and zero sequence) and neutral grounding impedances • High voltage transmission line impedances (positive and zero sequence) and mutual coupled impedances (zero sequence) • Generator impedances (saturated and unsaturated reactances that include direct and quadrature axis, negative and zero sequence impedances and their associated time constants) • Documentation showing the function of all protective elements listed above

General Data Exchange Requirements – Transmission or Distribution Owner Data and Information 16 16  The following general information must be exchanged in addition to relay settings to facilitate coordination, where applicable: • Relay scheme descriptions • Regional Reliability Organization’s off-nominal frequency plan • CT and VT/CCVT configurations • Any transformer connection configuration with transformer tap position(s) and impedance (positive and zero sequence) and neutral grounding impedances • High voltage transmission line impedances (positive and zero sequence) and mutual coupled impedances (zero sequence) • Documentation showing the function of all protective elements • Results of fault study or short circuit model • Results of stability study • Communication-aided schemes

Detailed Coordination Information for Functions 21 and 51V 17 17  Detailed coordination information is presented under seven headings, as appropriate, for each function in the document.  The following slides present a section-by-section summary for Functions 21 and 51V.

Document Format – Seven Sub-Sections for Each Protection Function 18 18  Purpose  Coordination of Generator and Transmission System • Faults • Loadability • Other Conditions, Where Applicable  Considerations and Issues  Coordination Procedure • Test Procedure for Validation • Setting Considerations  Examples • Proper Coordination • Improper Coordination  Summary of Detailed Data Required for Coordination of the Protection Function  Table of Data and Information that Must be Exchanged

Purpose – Function 21 19 19  Machine Only Coverage – Provide thermal protection of the generator for a transmission fault that is not cleared  System Trip Dependability – Provide relay failure backup protection for all elements connected to the GSU high-side bus

Coordination of Generator and Transmission System – Function 21 20 20  Faults • The detection of a fault is most easily demonstrated by an example. • In the example, it is assumed that a transmission line relay failure has occurred and the fault is at the far end of the protected line. • The example presents solutions that can be used to permit tripping for the fault while not tripping for non- fault conditions when the generator is not at risk.