Capacitor TrainingDuck River Electric Membership Corp.

Doug Simpson

Welcome and Introduction

CAPACITOR FUNDAMENTALS

CAPACITOR USES

DREMC Practices

Capacitor Safety

CAPACITOR FUNDAMENTALS

A capacitor is a device that accepts an electrical charge, stores it, and then releases the charge when desired.

A good comparison to a capacitor would be a battery.

CAPACITOR FUNDAMENTALS-Vocabulary

When talking about Capacitors…KVAR - is the “measure of” good offset a

capacitor will provide against bad inductance. It is not the name for a Capacitor, only a measurement.

The term Bank refers to each phase being involved just like with a transformer bank, A,B, & C.

CAPACITOR FUNDAMENTALS- What does a Capacitor consist of?

In its simplest form, a capacitor consists of two metallic plates separated by an air gap.

Only three factors govern how much energy can be stored in a capacitor.

1. How big are the plates?2. How close are they together?3. What insulating material separates

them?

CAPACITOR FUNDAMENTALS- What a Capacitor consists of continued…

Basically, the larger the surface of the metallic plates and the closer they are together, the more energy the capacitor can store.

If the space between the plates is filled with different insulating material, such as Kraft paper or oil, the capacity will be greater than with air.

CAPACITOR USES-What are the Primary uses for a Capacitor?

1. Improving Power Factor (or VAR Control).2. Reducing Line Losses (or VAR Control).3. Decreasing Voltage Drop.

DREMC uses Capacitors for VAR control on our system, not decreasing voltage drop.

CAPACITOR USES- Power Factor

Real power is usable power measured as kW(kilowatt).Reactive power is the unusable power measured as

kVAR (kilo Volt Amp Reactive).Apparent power is the true measured value on the

power system measured as kVA(kilo Volt Amp). It is made up of two components, real power (expressed in kW) and reactive power (expressed in kVAR).

(kW)

(kVAR)(kVA)

(kW)

(kVAR)(kVA)

kW² + kVAR² = kVA²

P² + Q² = S²

a² + b² = c²

S=Q=

P=

CAPACITOR USES- POWER FACTOR…

To understand what a capacitor does, you will have to understand what is meant by POWER FACTOR (pf).

Pf= Real Power(kW) = 1 (Ideal Case)

Apparent Power(kVA)

CAPACITOR USES- POWER FACTOR Continued…

Reactive Power

Real Power

Pf= Real Power = 1 (Ideal Case)Apparent Power

CAPACITOR USES- Line Losses and Voltage Drop

Imagine yourself at Point A wanting to get to Point C, but due to obstructions you must first walk to Point B and then to Point C. The energy you expended walking to Point C was increased because you could not take the direct course.

CAPACITOR USES- Line Losses and Voltage Drop Continued

Power Systems act just like our example. The reactive power ( the extra steps from Point B to Point C) makes the power system work harder. To offset the this reactive power, capacitors are added to the system to make Points B and C closer together. This makes the apparent power value closer to the real power value. Remember, the Ideal case is for the apparent power and the real power to equal each other. This would make the power factor equal 1.

CAPACITOR USES- Line Losses and Voltage Drop Continued

1. Equipment may have to work harder and will not last as long because of line losses. Capacitors help the equipment work better because the equipment is not overburdened and, in turn, will last longer

2. High kVAR demands cause excessive voltage drop. Capacitors help to correct this.

3. A low power factor may cause an unnecessary increase in system losses. Remember the ideal power factor is 1.

DREMC PracticesCAPACITOR BANK TYPES

FIXED BANKS- The Capacitor bank stays “online” all the time and should have operable load break fuse disconnects.

SWITCHED BANKS- On a circuit are switched as TIME/VOLT. This means the Capacitor bank switches on and off by TIME and can be over ridden by VOLTAGE either too high or too low. They must have operable “oil switches” on these banks.

DREMC PracticesCAPACITOR BANK TYPES

Fixed Capacitor Bank Switched Capacitor Bank

Load Break FuseDisconnect

“Oil Switch” (Vacuum)

DREMC PracticesCAPACITOR BANK TYPES

SUBSTATION SWITCHED BANKS-

Are switched at the Manchester 161 by a S&C Intellicap only on voltage at 8,100 kVAR each bank, switches 318 and 328.

Are switched at Unionville by a SEL relay on Power Factor normally and on VOLT when the Mobile is in service, because it does not have a LTC, at 1,800 kVAR each bank, switches 318, 328, 338, & 348.

DREMC PracticesCAPACITOR BANK SIZE MATH

DREMC stocks 100 kVAR and 200 kVAR capacitors

A 600 kVAR bank means that A, B, & C Ø each have one 200 kVAR capacitor mounted in the capacitor rack. 200 kVAR times 3 phases = 600 kVAR

DREMC PracticesBank Sizes and Proper Fusing

When Fusing both bank size and voltage will influence your proper choice.

7.2kV, 300kVAR bank= 20T fuse7.2kV, 600kVAR bank= 40T fuse14.4kV, 600kVAR bank= 20T fuse14.4kV, 1,200kVAR bank= 40T fuse

DREMC PracticesS&C Intellicap Operation Features

1. When manually opened or closed, the control will delay the intended action for a total of 30 seconds. USE THIS TIME TO GET IN A SAFE POSITION.

2. When opened automatically or manually, the control will block closing for 5 minutes total.

Capacitor Safety-Procedure

DANGER READ!1) OPEN CAPACITOR SWITCH.2) OPEN MAIN FUSES WITH AN

INSULATED STICK.3) WAIT 5 MINUTES.4) AFTER 5 MINUTES, BLEED OFF

CAPACITORS TO GROUND USING AN INSULATED STICK.

5) JUMPER BOTH BUSHINGS TOGETHER AND THEN TO TANK.

Capacitor Safety-Handling Procedures

• ALWAYS Ground the Capacitor with a heavy wire jumper from bushing to bushing to TANK to keep the capacitor SHORTED for SAFETY!

• Do not lift the capacitor by the bushings or shorting wire to keep from breaking the bushings for safe handling.

Capacitor Safety-Removing From Service

• ALWAYS utilize load break devices when removing a capacitor bank from service.

• USE A LOAD BUSTER TOOL WHEN YOU CAN FOR ANY MALFUNCTIONED LOAD BREAK DEVICE ON A CAPACITOR BANK, DO NOT ATTEMPT TO BREAK LOAD OTHERWISE!