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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.
Wiki User
∙ 11y ago
Wiki User
∙ 12y agoAs as rule of thumb, transformer differential protection is used for transformer rated 10MVA or more. The reason is practicality as the differential protection is expensive. For small rated transformer, the cost of differential protection is almost equal to the cost of the transformer being protected which is not practical. Remember that the protection is there to avoid or limit the damage to the transformer.
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Why differential relay is not used for 11kv transformers?
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.
What is defrential protection relay?
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.
What is biased differential protection realy?
this is additionl of differential realy......
How does the standby earth fault scheme work?
Restricted earth fault protection is used to protect a specific zone, and should not trip for a fault outside of that zone (usually limited to a transformer, and possibly extending to lowside, highside, and tertiary breakers). Stand by earth fault protection is a term I am not very familiar with, but I believe this would be protection that is meant for a specific zone as backup, and can operate for faults outside of this zone. An example might be a highside time overcurrent relay set looking into a transformer, where the transformer is protected by a differential (primary protection), and there is a lowside feeder with relays (primary protection). The highside overcurrent acts as a backup (secondary protection) for the transformer and the feeder, and is delayed due to the nature of a time overcurrent relay.
Which types of relay is use in power transformer?
A 'power transformer' is a category of transformer used within electricity transmission and primary distribution systems. Relays are widely used with power transformers to provide various types of protection that will act to disconnect the transformer in the event of a fault. Examples of these relays include Buchholz relays, earth-fault relays, and differential relays. Relays are also used to operate a power transformer's automatic tap-changing mechanism in order to compensate for changes in load.
Why percentage differential protection is preferred over differential protectionfor internal faults?
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
Why differential relay is not used for 11kv transformers?
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.
How differential protection work in a transformer?
Power flowing into a transformer must match the power flowing out (minus losses which are minimal). If this is not the case, there's something wrong. Differential protection monitors current only; Current flowing into one side of the transformer will be equal to current flowing out the other side scaled by the turns ratio of the transformer. Since the turns ratio is equivalent to the voltage ratio, this is easily set.
What is the definition of differential relay and how does it function?
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.
What is the differential between internal fault and external fault in transformer differential protection?
Internal Fault means, fault due to winding, insulation, core etc which are inner side of transformer. External fault means, Fault due to atmosphere Condition where transformer is placed moisture,dust, etc
Dear all what direct consequences can be from Current transformer on generator with respect to differential protection relay?
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.
What is defrential protection relay?
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.
What is linear transformer?
The Linear Variable Differential Transformer is a type of electrical transformer used for measuring linear displacement. A counterpart to this device that is used for measuring rotary displacement is called a Rotary Variable Differential Transformer.
Where you can see differential protective relay?
Power Transformer
What is biased differential protection realy?
this is additionl of differential realy......
What is lvdt?
The linear variable differential transformer (LVDT) is a type of electrical transformer used for measuring linear displacement.
What does the abbreviation LVDT stand for?
The abbreviation LVDT stands for "Linear Variable Differential Transformer". In common usage, it is also just called a differential transformer, and measures linear displacement, i.e. movement.
