Time Setting Multiplier MCQ Quiz - Objective Question with Answer for Time Setting Multiplier - Download Free PDF

Explanation:

The Time Setting Multiplier (TSM) of a Relay

The Time Setting Multiplier (TSM) is a critical parameter in the operation of protective relays, especially in the context of overcurrent and differential protection schemes. The TSM adjusts the time delay characteristic of the relay, which influences how quickly the relay responds to fault conditions. This adjustment is crucial for coordinating the protection devices within an electrical system to ensure selective tripping and minimize disruption to the power supply.

Analysis of Other Options:

Option 1: Adjust the Operating Current Threshold of the Relay

This option is incorrect because the operating current threshold, also known as the pickup current, is typically adjusted using the current setting parameter of the relay. The TSM is concerned with the time delay characteristics rather than the current threshold.

Option 2: Increase the Current Setting of the Relay

This option is incorrect as well. Increasing the current setting of the relay would mean changing the current level at which the relay starts to operate (pickup level), which is not the function of the TSM. The TSM specifically adjusts the time delay after the relay has picked up a fault current.

Option 4: Decrease the Time Delay of the Relay

While this option is partially correct, it is incomplete. The TSM can indeed decrease the time delay of the relay, but its primary function is to modify the time delay based on fault severity, meaning it can both increase and decrease the time delay as required for proper coordination. Therefore, option 3 is more comprehensive and accurate.

Concept:

The time multiplier setting (TMS) of a relay is given by:

\(TMS = {operating \space time \space of \space the \space relay\over operating \space time \space when \space TMS =1 \space }\)

Calculation:

Given, TMS = 0.2

When TMS = 0.7,then the operating time = 3 sec

For, TMS = 1, the operating time is \( {3\over 0.7}\) sec.

The operating time of the relay = \( {3\over 0.7}\times 0.2\)

t = 0.857 sec

Concept:

The plug setting multiplier of a relay is defined as the ratio of the secondary fault current to the pick-up current.

PSM = Secondary fault current/Relay current setting

Pick up current = (Rated secondary current in CT) x (Current setting)

Calculation:

Given that,

Current setting = 150% = 1.5

Relay CT ratio = 200/5

Rated secondary current = 5 A

Therefore, pickup value current of relay = 5 x 1.5 = 7.5 A

For 7.5 A, the current in the primary of the CT is \( = \frac{{200}}{5} \times 7.5 = 300\;A\)

Concept:

The plug setting multiplier of a relay is defined as the ratio of the secondary fault current to the pick-up current.

PSM = Secondary fault current/Relay current setting

Pick up current = (Rated secondary current in CT) x (Current setting)

Calculation:

Given that,

Current setting = 150% = 1.5

Relay CT ratio = 200/5

Rated secondary current = 5 A

Therefore, pickup value current of relay = 5 x 1.5 = 7.5 A

For 7.5 A, the current in the primary of the CT is \( = \frac{{200}}{5} \times 7.5 = 300\;A\)

Explanation:

The Time Setting Multiplier (TSM) of a Relay

The Time Setting Multiplier (TSM) is a critical parameter in the operation of protective relays, especially in the context of overcurrent and differential protection schemes. The TSM adjusts the time delay characteristic of the relay, which influences how quickly the relay responds to fault conditions. This adjustment is crucial for coordinating the protection devices within an electrical system to ensure selective tripping and minimize disruption to the power supply.

Analysis of Other Options:

Option 1: Adjust the Operating Current Threshold of the Relay

This option is incorrect because the operating current threshold, also known as the pickup current, is typically adjusted using the current setting parameter of the relay. The TSM is concerned with the time delay characteristics rather than the current threshold.

Option 2: Increase the Current Setting of the Relay

This option is incorrect as well. Increasing the current setting of the relay would mean changing the current level at which the relay starts to operate (pickup level), which is not the function of the TSM. The TSM specifically adjusts the time delay after the relay has picked up a fault current.

Option 4: Decrease the Time Delay of the Relay

While this option is partially correct, it is incomplete. The TSM can indeed decrease the time delay of the relay, but its primary function is to modify the time delay based on fault severity, meaning it can both increase and decrease the time delay as required for proper coordination. Therefore, option 3 is more comprehensive and accurate.

Concept:

The time multiplier setting (TMS) of a relay is given by:

\(TMS = {operating \space time \space of \space the \space relay\over operating \space time \space when \space TMS =1 \space }\)

Calculation:

Given, TMS = 0.2

When TMS = 0.7,then the operating time = 3 sec

For, TMS = 1, the operating time is \( {3\over 0.7}\) sec.

The operating time of the relay = \( {3\over 0.7}\times 0.2\)

t = 0.857 sec

Concept:

The plug setting multiplier of a relay is defined as the ratio of the secondary fault current to the pick-up current.

PSM = Secondary fault current/Relay current setting

Pick up current = (Rated secondary current in CT) x (Current setting)

Calculation:

Given that,

Current setting = 150% = 1.5

Relay CT ratio = 200/5

Rated secondary current = 5 A

Therefore, pickup value current of relay = 5 x 1.5 = 7.5 A

For 7.5 A, the current in the primary of the CT is \( = \frac{{200}}{5} \times 7.5 = 300\;A\)

Explanation:

The Time Setting Multiplier (TSM) of a Relay

The Time Setting Multiplier (TSM) is a critical parameter in the operation of protective relays, especially in the context of overcurrent and differential protection schemes. The TSM adjusts the time delay characteristic of the relay, which influences how quickly the relay responds to fault conditions. This adjustment is crucial for coordinating the protection devices within an electrical system to ensure selective tripping and minimize disruption to the power supply.

Analysis of Other Options:

Option 1: Adjust the Operating Current Threshold of the Relay

This option is incorrect because the operating current threshold, also known as the pickup current, is typically adjusted using the current setting parameter of the relay. The TSM is concerned with the time delay characteristics rather than the current threshold.

Option 2: Increase the Current Setting of the Relay

This option is incorrect as well. Increasing the current setting of the relay would mean changing the current level at which the relay starts to operate (pickup level), which is not the function of the TSM. The TSM specifically adjusts the time delay after the relay has picked up a fault current.

Option 4: Decrease the Time Delay of the Relay

While this option is partially correct, it is incomplete. The TSM can indeed decrease the time delay of the relay, but its primary function is to modify the time delay based on fault severity, meaning it can both increase and decrease the time delay as required for proper coordination. Therefore, option 3 is more comprehensive and accurate.

The plug setting of a relay is adjusted by changing the number of ampere turns. The ampere turns determine the sensitivity of the relay, as they are directly related to the current needed to activate the relay. By altering the number of ampere turns, the relay's operating threshold can be modified to ensure it functions correctly under different electrical load conditions.

\(Plug\;setting\;multiplier = \frac{{Fault\;current\;in\;realy\;coil}}{{Rated\;CT\;secondary\;currret \times current\;setting}}\) 

Given that for PSM = 5 and TSM = 2,

Operating time = 5 sec.

When PSM = 5, TSM = 0.5

Operating time \(= \frac{{0.5}}{2} \times 5 = 1.25\;sec\)

\(Time \propto TSM\)

For same value of PSM, operating time will be more which have high TSM.