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In the event of a busbar fault, the next level of protection will operate and disconnect the busbars.
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What is purpose of ct supervision relay in high impedance bus bar protection?
A high impedance bus bar relay uses summed CTs from multiple breakers into a high resistance to determine a fault condition. Since all CTs connect to a single input on the relay, the relay cannot determine if a valid fault condition has occured, or one of the CTs is disconnected (open circuited). External CT supervision must be supplied to confirm.
What is Power systems protection?
Primary and back-up protectionThe reliability of a power system has been discussed in earlier sections. Many factors may cause protec­tion failure and there is always some possibility of a circuit breaker failure. For this reason, it is usual to supplement primary protection with other systems to 'back-up' the operation of the main system and ensure that nothing can prevent the clearance of a fault from the system.Back-up protection may be obtained automatically as an inherent feature of the main protection scheme, or separately by means of additional equip­ment.Time graded schemes such as over current or distance protection schemes are examples of those providing inherent back-up protection; the faulty section is normally isolated discriminatively by the time grading, but if the appropriate relay fails or the circuit breaker fails to trip, the next relay in the grading sequence will complete its operation and trip the associated circuit breaker, thereby inter­rupting the fault circuit one section further back. In this way complete back-up cover is obtained; one more section is isolated than is desirable but this is inevitable in the event of the failure of a circuit breaker.Where the system interconnection is more complex, the above operation will be repeated so that all parallel infeeds are tripped.If the power system is protected mainly by unit schemes, automatic back-up protection is not obtained, and it is then normal to supplement the main protection with time graded over current pro­tection, which will provide local back-up cover if the main protective relays have failed, and will trip further back in the event of circuit breaker failure.Such back-up protection is inherently slower than the main protection and, depending on the power system configuration, may be less discriminative. For the most important circuits the performance may not be good enough, even as a back-up protection, or, in some cases, not even possible, owing to the effect of multiple infeeds. In these cases duplicate high speed protective systems may be installed. These provide excellent mutual back-up cover against failure of the protective equipment, but either no remote back-up protection against circuit breaker failure or, at best, time delayed cover.Breaker fail protection can be obtained by checking that fault current ceases within a brief time interval from the operation of the main protection. If this does not occur, all other connections to the bus bar section are interrupted, the condition being necessarily treated as a bus bar fault. This provides the required back-up protection with the minimum of time delay, and confines the tripping operation to the one station, as compared with the alternative of tripping the remote ends of all the relevant circuits.The extent and type of back-up protection which is applied will naturally be related to the failure risks and relative economic importance of the system. For distribution systems where fault clearanceTimes are not critical, time delayed remote back-up protection is adequate but for EHV systems, where system stability is at risk unless a fault is cleared quickly, local back-up, as described above, should be chosen.Ideal back-up protection would be completely independent of the main protection. Current trans-formers, voltage transformers, auxiliary tripping relays, trip coils and D.C. supplies would be duplicated. This ideal is rarely attained in practice. The following compromises are typical:a. Separate current transformers (cores and secondary windings only) are used for each protec­tive system, as this involves little extra cost or accommodation compared with the use of common current transformers which would have to be larger because of the combined burden.b. Common voltage transformers are used because duplication would involve a considerable increase in cost, because of the voltage transformers them-selves, and also because of the increased accom­modation which would have to be provided. Since security of the VT output is vital, it is desirable that the supply to each protection should be separately fused and also continuously supervised by a relay which will give an alarm on failure of the supply and, where appropriate, prevent an unwanted operation of the protection.c. Trip supplies to the two protections should be separately fused. Duplication of tripping batteries and of tripping coils on circuit breakers is sometimes provided. Trip circuits should be continuously supervised.d. It is desirable that the main and back-up protections (or duplicate main protections) should operate on different principles, so that unusual events that may cause failure of the one will be less likely to affect the other.Previous Next
How can you calculate the copper bus bar according to the amp?
To obtain the amp of the copper bus bar, multiply the width of the bus bar by the thickness of the bus bar to obtain the current carrying capacity of the bus bar.
What is the standard height over a breakfast bar for pendant lighting?
In the range of 28-34 inches above the breakfast bar. Lights should be centered width-wise on the bar.
What happens to voltage during a short to ground?
Basically, the same as if you had a short to neutral, since the neutral and ground are tied to the same bus bar in the breaker panel. The breaker should trip, or the fuse should blow. Supply of voltage then stops.See the answer to the Related Question about GFCIs - shown below - for information about circuit protection when even a small current flows to ground.
What is relay coil?
An electrical device, typically incorporating an electromagnet, which is activated by a current or signal in one circuit to open or close another circuit.Based on Characteristic the protection relay can be categorized as-Definite time relaysInverse time relays with definite minimum time(IDMT)Instantaneous relays.IDMT with inst.Stepped characteristic.Programmed switches.Voltage restraint over current relay.Based on of logic the protection relay can be categorized as-Differential.Unbalance.Neutral displacement.Directional.Restricted earth fault.Over fluxing.Distance schemes.Bus bar protection.Reverse power relays.Loss of excitation.Negative phase sequence relays etc.Based on actuating parameter the protection relay can be categorized as-Current relays.Voltage relays.Frequency relays.Power relays etc.Based on application the protection relay can be categorized as-Primary relay.Backup relay.Primary relay or primary protection relay is the first line of power system protection whereas backup relay is operated only when primary relay fails to be operated during fault. Hence backup relay is slower in action than primary relay. Any relay may fail to be operated due to any of the following reasons,The protective relay itself is defective.DC Trip voltage supply to the relay is unavailable.Trip lead from relay panel to circuit breaker is disconnected.Trip coil in the circuit breaker is disconnected or defective.Current or voltage signals from CT or PT respectively is unavailable.As because backup relay operates only when primary relay fails, backup protection relay should not have anything common with primary protection relay.Some examples of Mechanical Relay are-Thermal(a) OT trip (Oil Temperature Trip) (b) WT trip (Winding Temperature Trip) (C) Bearing temp trip etc.(a) Buchholz (b) OSR (c) PRV (d) Water level Controls etc.Float typePressure switches.Mechanical interlocks.Pole discrepancy relay.
The movable iron bar in a relay is called a what?
A relay is made up of a coil with an iron core and a movable iron bar. The movable iron bar in a relay is called a switch.
What is purpose of ct supervision relay in high impedance bus bar protection?
A high impedance bus bar relay uses summed CTs from multiple breakers into a high resistance to determine a fault condition. Since all CTs connect to a single input on the relay, the relay cannot determine if a valid fault condition has occured, or one of the CTs is disconnected (open circuited). External CT supervision must be supplied to confirm.
What is the iron bar in a relay called?
The armature.
About bus bar protection ques and ans?
Protection of busbars is mainly done using differential relays. These relays sense current flowing into the bus and current flowing out of the bus. If current in != current flowing out, the relay assumes there is a fault on the bus and trips breakers to isolate the bus.
The movable iron bar in a relay?
It is called an armature.
What is the moveable iron bar in a relay called?
The armature.
When did The Space Bar happen?
The Space Bar happened in 1997.
When did Battle of Bar happen?
Battle of Bar happened in 1042.
When did Bar Confederation happen?
Bar Confederation happened in 1768.
Bus bar differential protection relay?
SEL-387 (4 current sets), SEL-387B (6, can be combined with three units for total of 18), CA-16 is an older electromechanical type bus dif relay. I'm not familiar with other brands, but there are many others made by ABB, GE, etc.
A what consists of a coil with an iron core and a movable iron bar?
A relay.
