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What is burden in CT and PT?
The burden is the termination impedance of the measuring instrument. The measuring instrument can be an analog or digital energy meter, a data logger or a recorder. Technically, the total burden for a CT is the internal winding resistance, the connecting lead resistance and the measuring instrument input resistance.
How is VA burden of PT calculated?
For a control PT, choose a burden VA that is greater than, or equal to, 1.5 times the total combined VA of all the equipment being connected to the secondary side of the PT.
Why Pt burden is high compared with CT burden?
Also Potential transformers are higher in cost as compare with the current transformer. The cost will be reduced as the burden increases, instead of that if we go for New potential transformer for feature loads we have to install additional PTs.
What does PT stand for in electrical terms?
Voltage transformers (VT), also called potential transformers (PT), are a parallel-connected type of instrument transformer. They are designed to present a negligible load to the supply being measured and have an accurate voltage ratio and phase relationship to enable accurate secondary connected metering.
What does burden of CT mean?
Burden of CT is defined as the volt ampere loading which is permissible without errors exceeding the limits for an assigned accuracy class. It is expressed as volt ampere (VA). In simple words, it is the load connected to CT secondary.
What is burden for CT?
Burden of CT can be specified as Volt-Ampere absorbed at certain Power Factor i.e the VA that can be consumed by the load. The burden can also be expressed as total Impedance in terms of ohms connected on secondary of CT i.e. pilot conductor and instrument burden (I2 x R=VA). There are 2 types of CT.
What is Burden relay?
Explanation: Since burden is resistive element so it will always absorb power. This power is absorbed by relay circuit and is used to trip the circuit breaker. It is measured in V A (Volt – Ampere).
Why CT secondary should not be kept open?
If the primary circuit has current flowing the secondary circuit should never be opened. This can cause very high voltages to occur due to the Ampere-Turns of the primary that start magnetizing the core. While it is acting as a transformer it will cause very high voltage peaks. …
What is Burden resistance of CT?
The load, or burden, in a CT metering circuit is the (largely resistive) impedance connected to the secondary winding. Typical burden ratings for IEC CTs are 1.5 VA, 3 VA, 5 VA, 10 VA, 15 VA, 20 VA, 30 VA, 45 VA & 60 VA. ANSI/IEEE burden ratings are B-0.1, B-0.2, B-0.5, B-1.0, B-2.0 and B-4.0.
What is a PT in a substation?
Potential transformer is a voltage step-down transformer which reduces the voltage of a high voltage circuit to a lower level for the purpose of measurement. These are connected across or parallel to the line which is to be monitored. In common, the potential transformers are abbreviated as PT.
Why is PT connected in parallel?
PT needs to be connected in parallel because we need to measure the voltage. These are similar to voltmeter and Ammeter.
What is the difference between actual burden rating and burden rating?
Burden rating of the transformer provide s maximum value of apparent power, which the the transformer can provide under specified conditions. Actual burden is the actual value of apparent power, that is being drawn by the load from the transformer output.
What is the meaning of the burden of a transformer?
Burden is nothing but an output apparent power of the instrument transformer. The burden of the transformer is normally denoted in VA. VA means Volt Amp.
What is the total burden on the secondary of a CT?
The total burden on secondary is due to the relays, meters, connecting leads and resistance of secondary winding of CT. CT burden can be reduced by using low secondary current like 2 or 1 ampere. , Power system engineer who knows his stuff.
What is the thermal burden rating of a VA panel?
If no thermal burden in VA is given, the thermal burden rating in VA shall be the same as the maximum standard burden for which an accuracy rating is given. Referring to the name plate above, the thermal rating is 1,500VA at 30 deg C ambient or 1,000VA at 55 deg C ambient.