B. Mehraban, D. Reed, R. Gutman – AEP

B. Depommier, R. Hariharan, S.R. Mendis, S. Shah – ALSTOM Grid

SVC Refurbishment for Smart Grid Power Quality Enhancement and Life Extension

WG I4 Activities Related to SVC Refurbishment

• Special Publication – Static Var Compensator Refurbishment, July 2003.

• SVC Reliability Survey (On-going Work)

– To collect information from SVC owners/users on the availability and reliability of existing installations to quantify the number and causes for SVC outages.

2

WG I4 Activities Related to SVC Refurbishment 3

SVC Equipment and Sub-Systems Life Cycle Years

Control System 15 to 20

Protection System 20

Auxiliary System

Cooling System

Instrument Transformers

Air-Core Reactors and Capacitor Banks

Circuit Breakers and Instrument Transformers

Thyristor Valves

Coupling Transformer 40

Control Building 50

Roanoke SVC Summary 4

• SVC Commissioned: 1992

• Year of Refurbishment: 2012

• Site Location: Roanoke, VA

• SVC Rating: 170MVAR connected at 34.5kV

• SVC Application:

– Power Quality Improvement (power factor, voltage flicker and harmonic distortion) of 138kV network due to local meltshop (electric arc furnace) operation

– Voltage support for local electric arc furnace production

• Electric Furnace Load

– Electric Arc Furnace (EAF): 56 MVA

– Ladle Metallurgical Furnace (LMF): 17 MVA

Roanoke SVC Configuration 5

Thyristor Controlled Air-Core Reactors

Harmonic Filters

Thyristor Valve

SVC Control System

Determining Factors for Roanoke SVC Refurbishment 6

Power Quality Improvements:

– Reduce Voltage Flicker to within AEP Limit requirements at 138kV

– Reduce 2nd Harmonic Current Distortion and Total harmonic Current Distortion to within AEP Requirements at 138kV

Reliability and Availability Improvements:

– Aging of Equipment and Sub-Systems: Thyristor Controlled Air-Core Reactors (TCR), Thyristor Valves Components, Cooling System, 2nd Harmonic Filter Reactors and Capacitors

– Obsolescence of analog SVC Control System, Unavailability of Controls Spare Parts

Solution:

- Replace SVC Control System, Thyristor Valves, Thyristor Cooling System (pump station, heat exchangers, piping indoors and outdoors), SVC Controls, TCR Coils, and complete 2nd Harmonic Filter Bank

SVC Refurbishment Project Requirements 7

Voltage Flicker at 138kV:

– Short-term Flicker Severity Level (PST) ≤ 1.2 for 99% of the time

Harmonic Distortion at 138kV:

- Total Voltage Distortion THDV ≤ 2.5%

- Total Current Distortion THDi ≤ 6.0%

- 2nd Harmonic Current Distortion ≤ 5.0%

- Above Requirements to be met for 95% of the time

Reliability and Availability Improvements:

– Observation Period: 5 years

– Forced Energy Unavailability (FEU) not to exceed 2.0% annually (175.2 hours)

– Scheduled Energy Unavailability not to exceed 1.5% annually (131.4 hours)

– Forced Outages ≤ 4 for the first year and ≤3 per year for the remaining 4-years of the observation period

Time Schedule: - Not to Exceed 10 Months (from May 2012 to March 2013)

Project Approach 8

1. Perform on-site measurements prior to the upgrade (baseline)

2. Equipment Check/validation to review usability of existing equipment

3. Perform Design Studies (simulations) to validate performance

- Voltage Flicker

- Harmonic Distortion and Harmonic Filter Ratings

- Transient Studies

4. Develop Equipment Specifications for Procurement of new Equipment

5. Equipment Factory Acceptance Tests; SVC Control Testing on Real-Time Digital Simulator (RTDS)

6. Site Work: Removal of Old Equipment and Installation/Connection of New Equipment

7. Full SVC System Testing and Commissioning

8. Performance Validation Checks

Scope of Refurbishment Works 9

Remove and Replace

Scope of Refurbishment Works 10

Indoor Equipment Remove and

Replace

SVC Control System

Thyristor Valve and Cooling

System

Harmonic Studies 11

NEW

Before Upgrade After Upgrade

Transient Studies 12

Arc Furnace Transformer

Inrush at Energization

Voltages across 2H Harmonic Filter Reactor

Voltages across 2H Harmonic Filter Capacitor

Performance Verification – Voltage Flicker 13

Before Upgrade After Upgrade

PST(99%) = 1.56

PST(99%) = 1.11

Performance Verification – Harmonic Current Distortion 14

Before Upgrade After Upgrade

THDi(95%) = 8.7%

THDi(95%) = 6.0%

SVC Cooling System 15

New Outdoor Heat Exchangers

New Pump Station

SVC Outdoor Equipment 16

New Thyristor Controlled Air-Core

Reactors (TCR)

New 2H Harmonic Filter Bank

Conclusions 17

• This Project has demonstrated that a partial refurbishment of an SVC system is a suitable initiative, as opposed to a complete overhaul, that can extend the life of the entire system.

• Typically a refurbishment consists in replacing above-grade equipment and subsystems without affecting the existing foundations, control building, and below-grade trenches, conduits or grounding system.

• The first sub-system to be evaluated in priority is the SVC control system, which typically becomes obsolete after 15 to 20 years. With such obsolescence comes the issue of spare parts availability.

• The performance of the system, as well as its availability and reliability can be improved by switching to modern digital control systems and carefully designed new power equipment.

• Extensive system studies, testing and commissioning programs are required to ensure that the refurbished system will meet the new requirements.