China International Conference on Electricity Distribution ... · Introduction of 765 kV...

China International Conference on Electricity Distribution 2014 (CICED2014)Shenzhen, China

September 23 – 26, 2014

American Electric Power (AEP) Overview• Among the largest electric utilities in the

United States▫ Serving 5.3 M customers in 11 states▫ Total Assets $ 56 B▫ Generating Capacity 38 GW ▫ Electric Transmission Lines ~ 40,000 Mi.▫ Electric Distribution Lines ~ 215,000 Mi.

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$ 56 BASSETS

5.3 MCustomers

In 11 states

38 GWGeneration

40 KLine Miles OF Transmission

American Electric Power (AEP) Overview

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AEP Electric Transmission Infrastructure

• Owns and operates facilities in three RTO/ISOs through a variety of transmission companies• Supplies approximately 10% of the demand in

the Eastern Interconnection• Owns, operates, and maintains highest capacity

transmission in the USA ~2200 Mi. of 765 kV• Pioneer in transmission technology and

construction

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Regional Transmission Organizations (RTO)

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AEP Transmission History

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Introduction of 138 kV

Introduction of 765 kV

Introduction of 345 kV

1917 1953 1969

36 Years 16 Years

Power Supply Considerations• Safety• Reliability• Adequacy• Cost effectiveness and consistency• Resolve legacy issues• Enhance operational flexibility• Customer satisfaction• Compliance with codes and standards

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Transmission and Distribution Voltages

• Voltages 300 kV and above make up EHV• Voltages 100 kV and above considered as bulk

system and require adherence to NERC Standards/Criteria• Voltages below 100 kV classified as

subtransmission• Voltages 34.5 kV and 12 kV are typically

distribution – radial network8

Role of Transmission

• Analogous to the highway system▫ “Interstate Superhighways” for electric power to

move regionally and wide distances▫ Provides the foundation for robust and reliable electric

infrastructure▫ Connects large and remotely located generation

resources to the market ▫ Provides reliable exit points to serve load centers and

distribution networks

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Transmission Mission - AEP

• Assess the adequacy of AEP’s transmission on a continuous basis and formulate plans to:▫ Maximize asset value and utilization▫ Meet reliability standards and compliance

requirements▫ Meet the electrical demands of customers including

distribution

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AEP In-Line Switching Considerations• Switching arrangements at the tap point include:▫ Group Operated Air Break (GOAB) switch and not

part of the system automatic relaying scheme

▫ A GOAB switch equipped with automatic line sectionalizing capability is commonly referred as a “Motor Operated Air Break (MOAB) switch

▫ A Circuit Breaker (CB) provides high-speed automatic sectionalizing capability to make or break circuits and interrupt fault currents 11

Transmission and Distribution Interface Challenges• Transmission Station and Line Design▫ Switching arrangements, relaying, exposure,

interruptions, etc.▫ Lightning and grounding ▫ Shunt capacitor switching surges and harmonics▫ Voltage unbalance and reactive power supply ▫ Capacity/Adequacy

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Transmission and Distribution Interface Challenges (cont’d)• Distribution System Design▫ High side transformer switching Ground Switch/MOAB scheme CB, MOAB Switch, GOAB Switch, Fuses, etc.

▫ LTC vs Non-LTC▫ Power Factor, Capacitors, etc.▫ Distribution served from tertiary of Transmission

transformers

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Legacy Issues – T&D Interface

• In-Line switching inadequacy in connecting Distribution▫ Hard tap ▫ Manual switching ▫ Automatic switching without circuit breakers▫ Limited installation of circuit breakers• MOAB ground switch combination on the high

side of step-down transformers• Radial vs looped service • Power Factor at the interface

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Tap Station Definition and Functionality

• Any connection that results in only the associated load flowing through the connecting facilities under all conditions – radial▫ Radial line from an existing station or new station▫ Radial line from an existing or new transmission line

• Establishment of in-line facilities to carry transmission power flows in addition to radial load

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Transmission In-Line Switching Guidelines to Connect Load• GOAB manual switching – basic plan and minimum

requirement• MOAB automatic switching – based on the calculation

of Forced Outage Index (FOI)▫ FOI =Load (L) X Miles of Exposure (M) X Permanent Forced Outage Rate

(P) L = Peak load (in MW) that is directly jeopardized by the forced outage of the

subject line M= Number of miles between two existing automatic sectionalizing devices

(MOABs or CBs) plus new tap line length P = Permanent forced outage rate of the subject line (outages/year/mile)

▫ Install MOAB switches if “FOI” is equal to or greater than six (6)Note: Some exceptions are applicable on a case by case basis

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Transmission In-Line Switching Guidelines to Connect Load (cont’d)• Circuit Breaker (CB) – based on the calculation of

Momentary Permanent Outage Index (MPOI)▫ MPOI = Load (L) X Miles of Exposure X Forced Outage Rate

(Permanent Forced Outage Rate (P) + Momentary Forced Outage Rate(M))

▫ Install a CB if “MPOI” is equal to or greater than 200

Note: Some exceptions are applicable on a case by case basis including if power quality is a major concern due to forced momentary outages

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T&D Interface Transformer Switching• No MOAB ground switch combination on the

high side of transformers▫ Eliminate forced outage of the transmission line

connected between CB terminals; avoid interruption of customers served from the intermediate tapped stations

• No high side fuses on transformers greater than 10 MVA served from 69 kV or below ▫ Above 69 kV, no fuses; high speed protection (CBs or

similar devices) required 18

Looped Service vs Radial Service

• In general, looped service for Distribution load in excess of 30 MW▫ Consistent with the typical large size Distribution

transformer (30 MVA) ▫ Second transformer added when the load approaches

20 - 30 MVA

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T&D Interface Requirements

• No undue burden on the transmission system with respect to reactive power▫ Close to unity PF – AEP criteria is 99% PF

• Elimination of unacceptable transient voltages and harmonic resonance conditions due to capacitor switching – comply with IEEE standards

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Q & A

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