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Questions and Answers

What is the primary purpose of a reactor control system in an electrical power distribution system?

To regulate the voltage of the system by changing the amount of current flowing through the reactor (correct)

To provide a path for current to flow in the event of a fault

To improve the power factor of the system by reducing the amount of reactive power

To protect the system from overloads by limiting the amount of current that can flow

Which of the following is NOT a type of on-load tap-changer (OLTC) mentioned in the content?

GE LRT

Westinghouse URS

ABB SACE (correct)

Allis TLS

What is the purpose of a non-bridging position in an OLTC?

To allow for the tap changer to be disconnected from the system during maintenance (correct)

To prevent the tap changer from being switched to a position that would cause an overload on the system

To ensure that the tap changer can be switched to a different tap position without interrupting the flow of current

To provide a point of reference for the tap changer when it is switched to a new position

How often should the door gasket of an OLTC be replaced based on the information provided?

Every 1,000 operations Signup and view all the answers

What is the most likely reason for replacing the Geneva gear and helical gear in an OLTC with a helical gear with a 10 mm roller pin?

To reduce the wear and tear on the tap changer Signup and view all the answers

What is the significance of the number of tap change operations performed in the maintenance of an OLTC?

It dictates the frequency of maintenance required for the OLTC Signup and view all the answers

Which of the following is a possible benefit of using an OLTC in an electrical power distribution system?

Improved voltage regulation Signup and view all the answers

Which of the following companies is NOT listed as a performer of OLTC retrofits?

ABB Signup and view all the answers

What should be done first before disconnecting the wires from the current transformer (CT)?

Take loose the clamp from CT Signup and view all the answers

Which of the following tools is required to remove the nuts and bolts from the assemblies?

10mm wrenches Signup and view all the answers

What is the purpose of using the old fiber optic cable during installation of the new cable?

To pull the new one through the conduit Signup and view all the answers

When securing the fiber optic cable and CT lead, which tool is specified for tightening the clamp?

10mm wrenches Signup and view all the answers

What is the last step mentioned for connecting the current injection tester to the CT?

Connect the tester to 110v AC Signup and view all the answers

What safety measure should be taken before pulling the new fiber optic cable through the conduit?

Ensure the wires are disconnected Signup and view all the answers

Which colors correspond to the wires that need to be reconnected after the installation?

Orange, Blue, Green Signup and view all the answers

How should the fiber optic cable be secured to ensure it remains in place?

With wire ties and rubber pads Signup and view all the answers

In the context of the provided content, what is the primary function of the "variable CT" connected to bus bar P2 and the stationary contact (A) of the V.I. (vacuum interrupter) during the operational tripping test?

To simulate a fault condition on the bus bar P2, triggering a tripping event. Signup and view all the answers

When referring to a "VIM system", as mentioned in the provided content, what does "VIM" most likely stand for in the context of power systems?

Voltage Interrupter Mechanism Signup and view all the answers

Based on the content provided, what is the significance of bringing the "VIM system" into "maintenance mode" before performing LTC operations with the transformer deenergized?

To prevent the VIM system from interfering with the LTC operation and potentially causing damage. Signup and view all the answers

When the text states to "check fiber optic cables for possible damage", which aspect of the monitoring system is being assessed, and why is it important?

Electrical power distribution, to confirm the integrity of the network for transmitting control signals. Signup and view all the answers

The content mentions "ring-out copper conduits to ground". Which component's function is being assessed during this procedure, and what is the primary objective of this assessment?

Monitoring system, to confirm the integrity of the ground fault protection circuitry. Signup and view all the answers

In the context of the provided content, what is the main purpose of the "hi-pot test" performed on the vacuum interrupter?

To test the ability of the vacuum interrupter to withstand high voltage conditions. Signup and view all the answers

What is the main purpose of the "non-bridging position" mentioned in the text, and why is it important?

To isolate the vacuum interrupter from the power system during the hi-pot test. Signup and view all the answers

What is the significance of the "flexible connector" at P3 being removed before performing the hi-pot test on the vacuum interrupter?

To ensure the hi-pot test voltage is applied directly to the vacuum interrupter without interference. Signup and view all the answers

Study Notes

Wire Tie Pullers and Current Injection Tester Procedures

Remove all nuts and washers from the LTC door for future use.
Disconnect Orange, Blue, and Green wires from Current Transformer (CT).
Loosen the CT clamp using an 8mm wrench and 10mm wrenches for nuts and bolts.

Assembly and Cable Handling

Record the number or location of each wire before disconnection.
Disconnect Black, White, and Brown wires from the junction plate using appropriate screwdrivers.
Use existing fiber optic cable to pull new cable through the conduit, ensuring a hook is formed from wires and gently taped.
Reconnect the fiber optic cable to the junction plate at the correct terminal.

Securing and Reconnecting Components

Secure fiber optic cable with wire ties and rubber pads on both sides of P2 and P3.
Secure CT lead and fiber optic cable with clamps using 10mm wrenches.
Route the fiber optic cable through the clamp and secure with 8mm wrenches.
Reconnect Orange, Blue, and Green wires after securing all components.

Current Injection Tester Setup

Connect leads from the current injection tester to the CT, placing one lead on top and one on the bottom.
Connect the tester to a 110v AC power source.

Maintenance and Retrofit Procedures

Identified entities for retrofit maintenance include Siemens, GE, Allis, Federal Pacific, and several others.
Various transformer types are involved such as Westinghouse (URT, UTT), GE (LRT), and others.

On-Load Tap-Changer (OLTC) Maintenance

Replacement intervals for OLTC components depend on the number of operations performed; no time-based criteria exist.
Specific components like door gaskets, silica gel, and front plates must be replaced after specified operations, while Geneva gear requires a helical gear change at the next maintenance.

Vacuum Interrupter Testing Procedure

Insulating panel must be placed between the vacuum interrupter and support before testing.
Apply hi-pot test voltage of 25 kV AC or 30 kV DC for one minute for each vacuum interrupter.
Reconnect bus bars and fiber optic cable after testing.

Monitoring System Tests

Check fiber optic cables for damage and ensure conduits are secure in support clamps.
Verify operational status of the monitoring system by checking for illuminated LED indicators.

Operational Tripping Tests

Perform tests to ensure the monitoring system operates correctly by raising CT to produce 15 to 20A and activating the motor drive mechanism.
Enter “maintenance mode” for the VIM system before performing LTC operations while the transformer is de-energized. This is done by pressing the red button for 5-6 seconds until LEDs flash.

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