Transmission & Distribution Program

Electric Grid Operations TADP 543

Review Elements of the

Electric Power Grid

Module 3.1

Instructor: Julie Reichle

Audio: Marc Patterson

Introduction

This module presents:

The WECC standards and describes how the balancing authorities adhere to them.

Responsibilities and authorities specified by NERC standards, tools and data required for reliability coordinators, methods of operations planning and current day operations, and the methods for transmission loading relief.

What will be Learned

• How to analyze the transmission system and

determine if it meets NERC/WECC reliability

requirements and compliance standards.

• To do this, you will need to have a detailed

understanding of the NERC/WECC Reliability

Standards

Review Definitions and Terms

Before we start reviewing the standards we need to

review some definitions and terms.

Operational Constraints

• One of the keys to maintaining proper functioning of the grid is to operate within voltage boundaries.

• In addition, connected load and generation must match in order to maintain proper frequency.

• If the load is greater than generation the frequency will decrease.

• If generation is greater than load the frequency will increase.

Voltage and Frequency Control

Terms on the following pages are used in this

class.

Knowing these definitions will help you understand

our voltage control and frequency discussions.

Ampere

The unit of measurement of electrical current. One

Ampere is the unit of current produced in a circuit

by a potential of one volt acting through a one

ohm resistance.

Capacitance

Property of an electrical circuit which opposes any

change of voltage - developed when two conductors

are separated by a dielectric.

Measured in farads or microfarads (μf).

Capacitor

A device used to introduce capacitance into a

circuit. They are typically switched on and off with

a breaker.

Shunt

Property of an electrical circuit which produces an

electromotive force (emf) by induction when the

current is changing. Inductance opposes current

changes and is measured in Henries (h).

Inductance

Inductor

A device, usually a coil, which introduces

inductance into a circuit.

Load Diversity

Difference between the sum of the maximums of

two or more individual loads and the coincident or

combined maximum load.

Load-Tap-Changer (LTC)

A means to mechanically change transformer

winding taps without de-energizing the transformer.

Power Factor

Cosine of the difference in phase angle between

voltage and current (or real and apparent power) in

an electrical circuit.

Reactance

Opposition (in Ohms) to current flow caused by the

inductance and/or capacitance of an AC circuit.

Reactance is dependent upon both frequency and

circuit inductance and/or capacitance. Inductive

reactance is denoted XL and capacitive reactance

XC.

Reactor

A coil used to introduce inductance into an AC

circuit. In power systems they are typically

switched on and off through a circuit breaker.

Shunt

Resistance

The property of materials that hinders the flow of

electrical current

Static VAR Compensator (SVC)

A system of capacitors and reactors controlled by

solid state electronics to be a rapidly deployed

Source or Sink of reactive power (VARs).

Volt-Amperes Reactive (VAR)

The unit of measurement of reactive power

• f = frequency in Hertz

• L = inductance in Henries

• C = capacitance in farads

Reliability Standards

Reliability Standards

– GENERATION CONTROL AND PERFORMANCE

– TRANSMISSION

– INTERCHANGE

– SYSTEM COORDINATION

– EMERGENCY OPERATIONS

– OPERATIONS PLANNING

– TELECOMMUNICATIONS

– OPERATING PERSONNEL AND TRAINING

ACE

Area Control Error (ACE) is the algebraic sum of

the net scheduled and net actual interchange and

the Biased scheduled and actual system

frequency.

ACE is used to determine a control area’s

performance with respects to its impact on system

frequency

CPS

Control Performance Standard (CPS)

Each control area shall monitor its control

performance on a continuous basis against two

Standards: CPS1 and CPS2.

CPS1

CPS1 assigns each Control Area a slice of

responsibility for control of the Interconnection

frequency.

CPS1 is a yearly standard that measures impact

on frequency error, with a 100% minimum score.

Over a year, the average of clock-minute averages

of a control area’s ACE divided by -10β (β is

control area frequency bias) times the

corresponding clock-minute averages of

Interconnection’s frequency error shall be less

than a specific limit.

CPS2

CPS2 is a monthly standard that limits

unscheduled flows.

The minimum CPS2 score is 90%.

The average ACE for each of the six, ten-minute

periods during the hour (the ten-minute periods

ending at 10, 20, 30, 40, 50, and 60 minutes past

the hour) must be within specific limits, referred

to as L10.