Pad-Mounted Transformers & Switchgears

List 3 functions of the oil in the tank of a pad-mount transformer:

Insulate the windings; Cool the windings; Keep moisture from accumulating.

A pad-mount transformer may be classified as either ____ or ____, depending on how many connections are made between the primary URD cable and the transformer’s primary bushings.

Dead-Front; Live-Front

A fuse of a pad-mount transformer both ____ the URD system from faults and serves to ___ the primary windings to the bus bar.

Protects; Connects

______ vary the number of turns on a transformer’s primary windings, which affects the secondary voltage output.

Tap Changer/Tap Adjuster

A typical transformer installation includes the following steps (site prep):

Preparing the pad and the earth for the proper set; Terminating the cables after the transformer has been set; Testing the transformer for the proper voltage.

4 types of Arc-Suppressing mediums

SF6 Gas; Oil; Air; Vaccum

True or False; Cable trenches are typically dug before a pad-mount transformer is installed

True

Transformer connections are made at 3 locations:

At the connection of the primary feeder circuit; at the transformer; at the customers’ connection point.

A cable’s phase may be identified with marking directly on a cable jacket or by using ___.

Colored Tape

After a pad-mount transformer is installed, it is tested to make sure that it is supplying the the proper ___.

Secondary Voltage

True or False; Troubleshooting a pad-mount transformer can be difficult, because different problems can produce similar or confusing symptoms

True

Induction in the core can affect voltage readings in transformers with a ____ core construction.

Common

When troubleshooting a transformer, it is important to take a complete set of ____ readings and, in some cases, ____ readings.

Voltage; Load

True or False; Replacing a blown fuse usually takes care of a transformer problem

False

True or False; Troubleshooting a transformer often involves narrowing down a problem by correctly interpreting voltage and amperage readings.

True

By checking the customer’s breaker panel and finding normal secondary voltage readings, the crewman in the video demonstration was able to rule out both ____ and ____ as possible causes of the customer’s problem.

Off-Ratio Winding; Ferroresonance

As a safety precaution, a visual inspection of the ____ of a pad-mounted transformer may be conducted before the transformer is opened.

Exterior

____ were used to confirm periodic voltage fluctuations to the transformer’s secondary phases.

Voltage Recorder

The purpose of a pad-mounted switchgear is to ____ power through a main feeder system and provide ____ and ____.

Sectionalize; System Flexibility & Protection

A pad-mounted switchgear can be characterized as 2 things:

If it is life-front or dead-front; By the type of arc-extinguishing medium

An oil-immersed disconnect switch is divided into three main compartments: a ____ and two ____ ____

Tanks; Termination Conpartments

True or False; A transclosure provides a fused switching point for equipment and cables in a URD system

True

True or False; The inspection of a pad-mounted switchgear does not require opening the cabinet.

False

True or False; a pad-mounted switchgear is commonly used to reroute power or to isolate equipment to be taken out of service for maintenance.

True

Ferroresonance

A condition that occurs when the capacitance of the URD cable between a transformer and a blown fuse closely resembles the magnetic characteristics of the transformer core; occurs only in three-phase transformers with a common core construction