What is bus differential?

Bus differential, which is the most sensitive and reliable method for protecting a substation bus, is installed at transmission and distribution substations and switchyards. Overcurrent protection may be used for bus protection at lower voltage substations.

Which protection system is used for busbar?

The differential protection scheme is used both for the protection of the phase-to-phase fault and for the ground fault. Schematic diagram of bus differential protection relay is shown in the figure below. The current transformers are placed on both the incoming and the outgoing end of the bus-bar.

What do you mean by differential protection?

Differential protection is a unit-type protection for a specified zone or piece of equipment. It is based on the fact that it is only in the case of faults internal to the zone that the differential current (difference between input and output currents) will be high.

What are the problems in bus zone differential protection?

What are the problems in bus zone differential protection? _ Large number of circuits, different current levels for different circuits for external faults. _ Saturation of CT cores due to dc component and ac component in short circuit currents. The saturation introduces ratio error.

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Why is differential protection used?

Differential protection schemes are mainly used for protection against phase-to-phase fault and phase to earth faults. The differential protection used for power transformers is based on Merz-Prize circulating current principle. Such types of protection are generally used for transformers of rating exceeding 2 MVA.

Why busbar protection is required?

Busbars are very critical elements in a power system, since they are the points of coupling of many circuits, transmission, generation, or loads. So a high-speed bus protection is often required to limit the damage on equipment and system stability or to maintain service to as much load as possible.

What is the difference between busbar protection and LBB protection?

Fault occurs and say one of the Protection Relay Operates. If the Fault is cleared within 200ms, the LBB Scheme is Reset, but if the Fault is not cleared, LBB Operates. When the LBB Operates, it Trips, all the feeders on the concerned Bus with the help of Busbar Tripping Circuit.

What are the different types of busbar arrangements?

Types of Electrical Bus bar System

  • Single Bus-Bar Arrangement.
  • Single Bus Bar Arrangement with Bus Sectionalizing.
  • Main and Transfer Bus Arrangement.
  • Double Bus Double Breaker Arrangement.
  • Sectionalized Double Bus Arrangement.
  • One-and-a-Half Breaker Arrangement.
  • Ring Main Arrangement.
  • Mesh Arrangement.

What is high impedance busbar protection?

High impedance protection system is a simple technique which requires that all CTs used in the protection scheme have relatively high knee point voltage, similar magnetizing characteristic and the same ratio. These CTs shall be installed in all ends of the protected object.

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How CT is used for protection?

Protection CT This enables the protective relays to measure fault currents accurately, even in very high current conditions. The secondary current is used to operate a protective relay which can isolate part of the power circuit experiencing a fault condition.

What is biased differential protection?

What is the biased – differential protection. Biased – differential protection is an older design of protection than high impedance circulating current. It is widely applied to two-winding transformers except those connected to the lower distribution voltages.

Where is the plug setting multiplier?

Plug setting multiplier is nothing but a ratio between the actual fault current in the relay operating coil to pick up current (the relay current setting ). In other words, the ratio between the CT (current transformer) secondary current to relay operating current is called plug setting multiplier (PSM).

What is a bus coupler used for?

Bus coupler is a device which is used to couple one bus to the other without any interruption in power supply and without creating hazardous arcs. Bus coupler is a breaker used to couple two busbars in order to perform maintenance on other circuit breakers associated with that busbar.

How does busbar differential protection work?

Current Differential Protection. The scheme of busbar protection, involves, Kirchoff’s current law, which states that, total current entering an electrical node is exactly equal to total current leaving the node. Hence, total current entering into a bus section is equal to total current leaving the bus section.

What is end zone protection?

A fault occurs between the spot. The fault become cleared. Due to the fault in the dead spot zone, The relay initiates the high speed tripping signal to the remote circuit breaker instead of the local breaker such a protection is called end fault protection.

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