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Major Substation Equipment – Learn the Purpose, Cost, and Lead Time to Procure

By Aleen Mohammed / October 11, 2019 / 1 minute of reading

Are you fascinated by the equipment inside the substation? Use this resource to learn about major substation equipment.

Start with the power transformer image below.

Think you have this covered? Test your knowledge, attempt the quiz at the end of this post.

Power Transformer — Transformer

Circuit Breaker

Disconnect Switch

Circuit Switcher

Voltage Transformer — Capacitor Voltage Transformer

Current Transformer

Capacitor Bank

Gas Insulated Substation

Current Limiting Inductor — Inductor

Surge Arrester

Wavetrap — Wave Trap

Insulator

Knowledge Check

/7

Major Substation Equipment - Learn the Purpose, Cost, and Lead Time to Procure 1

Substation Major Equipment

It's only stupid-simple, let's begin.

You are building an interconnect station, tying wind farm generation to the power grid. At the substation, the sources are tied through a tie-breaker. Which device would you install to make sure the sources are synchronized?

Question Image

Power transformer

Voltage transformer

Current transformer

Ideal transformer

A synchronization check is done using a relay. It needs low voltage input (from both sides), obtained using a voltage transformer a.k.a. instrument transformer. Learn more.

A synchronization check is done using a relay. It needs low voltage input (from both sides), obtained using a voltage transformer a.k.a. instrument transformer. Learn more.

A transformer develops an internal fault. Which device would you install on the transformer high-side to interrupt fault current?

Question Image

Either a breaker or a circuit switcher

Disconnect switch

Circuit switcher

Circuit breaker

Both the breaker and the switcher have an interrupting chamber that can safely interrupt the fault current. A switch does not. A switch will draw an arc, that is damaging and a safety hazard. Learn more about switches here and circuit switchers here.

Both the breaker and the switcher have an interrupting chamber that can safely interrupt the fault current. A switch does not. A switch will draw an arc, that is damaging and a safety hazard. Learn more about switches here and circuit switchers here.

In a distribution substation, the available ground-fault current on the low side of the step-down transformer is excessive, over-dutying the switching equipment. What is your cost-effective solution to reducing the fault current?

Question Image

Add series inductors

Buy new transformer with higher impedance (%Z)

Add inductor in the transformer neutral

Add current limiting fuses in series on the switchgear

All methods mentioned help with limiting the fault current. The cheapest though is a neutral inductor, especially when mounted directly on the transformer. Learn more.

Current limiting fuses directly on the transformer secondary are rare. Mostly because of the continuous current requirement (1000amps or more) - fuses are rarely fabricated this large. This was a trap answer.

All methods mentioned help with limiting the fault current. The cheapest though is a neutral inductor, especially when mounted directly on the transformer. Learn more.

Current limiting fuses directly on the transformer secondary are rare. Mostly because of the continuous current requirement (1000amps or more) - fuses are rarely fabricated this large. This was a trap answer.

What's the purpose of a conventional power transformer?

Question Image

Transform power, voltage, and current

Transform voltage and current

Transform voltage only

Transforms voltage and current only. Power remains the same on both sides. Learn more.

Transforms voltage and current only. Power remains the same on both sides. Learn more.

An industrial facility is plagued with voltage flicker (due to harmonics) and poor power factor at the service entrance. Which device would you install to fix both issues?

Question Image

Install capacitor bank

Harmonic filter bank

Voltage regulator

Cap bank fixes the poor power factor only. It does provide a low impedance path for harmonics but it is not tuned to filter them out. A regulator does not remove the harmonics and neither does it fix the power factor. A filter bank addresses both - it is made up of inductors and capacitors therefore tunable and also capable of releasing VARs. (Note: one manifestation of harmonics is voltage flicker). Learn more.

Cap bank fixes the poor power factor only. It does provide a low impedance path for harmonics but it is not tuned to filter them out. A regulator does not remove the harmonics and neither does it fix the power factor. A filter bank addresses both - it is made up of inductors and capacitors therefore tunable and also capable of releasing VARs. (Note: one manifestation of harmonics is voltage flicker). Learn more.

Which combination of devices would you use to implement power line carrier?

Question Image

Wave trap, capacitor voltage transformer and line tuner

Wave trap and line tuner

Wavetrap, capacitor coupled voltage transformer, and line tuner

You need a device that allows a certain frequency to pass (CCVT and line tuner) and a device that stops it (wavetrap). Note a capacitor voltage transformer does not come with coupling accessories as such it does not work for transmitting carrier frequencies.

Click here for more detail on wavetrap and here for CCVT.

You need a device that allows a certain frequency to pass (CCVT and line tuner) and a device that stops it (wavetrap). Note a capacitor voltage transformer does not come with coupling accessories as such it does not work for transmitting carrier frequencies.

Click here for more detail on wavetrap and here for CCVT.

For which event should a surge arrester operate? Check all that apply.

Question Image

Lightning strike

Switching surge

Temporary overvoltage

Phase-to-ground short-circuit

Surge arresters are specified to discharge lightning strikes and switching surges. The equipment/system insulation can handle temporary overvoltage. Learn more.

Surge arresters are specified to discharge lightning strikes and switching surges. The equipment/system insulation can handle temporary overvoltage. Learn more.

Your score is

The average score is 41%

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Aleen Mohammed

Aleen Mohammed

Professional Engineer (Electrical)

Skillset: Substation Design | Power System Studies | Arc Flash Study

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