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I am going to assume that you are asking about a differential relay. It is basically just that- it compare two different sources and will trip at a set value value of the difference. These can be directional as well. A couple of examples are transformer protective relays and bus differential. A transformer relay will measure the amount of current coming into the transformer and the amount of current going out. If there is a disparity due to an internal fault the relay will trip the supply source and deenergize the transformer. Same for the Bus differential.
It depends what you mean by an '11-kV transformer'; do you mean a primary transformer (33/11-kV transformer) or a distribution transformer (11-kV/400-230-V transformer). Differential protection IS offered on primary transformers.
The current input (primary) to a transformer is proportional to the output (secondary) current. Differential protection relays monitor these via current transformers (CT). The percentage of difference between primary and secondary can be adjusted. If it is over the seting the relay will trip the primaryand secondary feeder breakers. Thus indicating an inbalance between internal phasewindings and or shorts to earth.
function of capacitive voltage transformer is measure high transmission voltage with low range voltmeter and oprate the relay circuit to oprate CBs.
A major cause of decomposition of transformer oil is minor arcing within the transformer. Decomposition results in gas which bubbles towards the top of the transformer and upward into the conservatory tank. Between the transformer and conservator tank is a Buchholz relay, in which this gas collects, causing a mercury switch inside a float to initiate an alarm in the substation. This gas can be collected through a small pipe feeding from the Buchholz relay in order to have it analysed.
In power transformer, a differential relay is a relay that verifies the balance of current between the primary and the secondary face of a transformer. It is also employed in other components of the power system like in protecting cables. Differential relay is also called a unit protection.
Power Transformer
I am going to assume that you are asking about a differential relay. It is basically just that- it compare two different sources and will trip at a set value value of the difference. These can be directional as well. A couple of examples are transformer protective relays and bus differential. A transformer relay will measure the amount of current coming into the transformer and the amount of current going out. If there is a disparity due to an internal fault the relay will trip the supply source and deenergize the transformer. Same for the Bus differential.
It depends what you mean by an '11-kV transformer'; do you mean a primary transformer (33/11-kV transformer) or a distribution transformer (11-kV/400-230-V transformer). Differential protection IS offered on primary transformers.
CT's are used as inputs to the differential. If the CT is bad, or it is not wired to the differential correctly, it will cause differential current to be seen by the relay, resulting in a trip.
A Buchholz relay is designed to detect a failing oil-filled power transformer. It will automatically disconnect the transformer and produce an alarm signal.
The current input (primary) to a transformer is proportional to the output (secondary) current. Differential protection relays monitor these via current transformers (CT). The percentage of difference between primary and secondary can be adjusted. If it is over the seting the relay will trip the primaryand secondary feeder breakers. Thus indicating an inbalance between internal phasewindings and or shorts to earth.
an REF relay (restricted earth fault) is used to provide ground fault protection for a transformer. Its' operation is limited by CTs starred towards the transformer (usually on the transformer bushings or in breakers used to isolate the transformer), so it will only operate for transformer related faults. Because of this, it can be set to operate very quickly.
function of capacitive voltage transformer is measure high transmission voltage with low range voltmeter and oprate the relay circuit to oprate CBs.
if we are seeking for internal protection of transformer only, then if any external fault occurs then it will show the fault though it should not. what a percentage differential protection will do means, it will include a restraining coil which is excited by the current in the transformer itself. Also the percentage differential relay ha taps. So it is easy to avoid the external fault. for reference check 'theory and applications of transformer differential protection' by GEORGE W.McKENNA, AIEE transactions 1950,volume 69
To enable any gases generated within the transformer to bubble along the pipe towards the expansion tank. The Buchholz relay itself isn't angled; it's the pipe in which its fitted.
A major cause of decomposition of transformer oil is minor arcing within the transformer. Decomposition results in gas which bubbles towards the top of the transformer and upward into the conservatory tank. Between the transformer and conservator tank is a Buchholz relay, in which this gas collects, causing a mercury switch inside a float to initiate an alarm in the substation. This gas can be collected through a small pipe feeding from the Buchholz relay in order to have it analysed.