What is biased differential relay

Basics and protection applications of low-resistance bus differential relays

Consequences of the busbar fault

Power system bus bars are electrical nodes that connect multiple circuits such as transmission lines, transformers, and generators together. Although the likelihood of a busbar failure is much lower than that of other parts of a power system if it does occur, it causes serious consequences for the entire electrical network.

Basics and protection applications of low-resistance bus differential relays

High-speed selective bus protection can go a long way in limiting the effects of a busbar fault on the system.

An innovative microprocessor based busbar differential relay that provides fast and sensitive operation under internal fault conditions and ensures improved stability in the event of external faults is presented. The relay is of low resistance with a biased differential characteristic and contains means for detecting the CT saturation.

The relay contains two separate bus differential zones to accommodate different bus sections using a dynamic bus copy mechanism that allows buses to be protected with circuitry that can be interconnected between different sections.

introduction

Busbars are connected to a number of energy sources, all of which generate very large fault currents in the event of a short circuit on the bus. On the one hand, failure of the protection to rectify an internal bus error can cause extensive damage and impair the stability of the network system.

On the other hand, it's just as harmful to you To work busbar protectionbecause an important node will then be removed from the network, which can also disrupt the operation of the entire electricity network.

Example bus configuration. Double bus arrangement with NORTH and SOUTH buses, five circuits and a tiebreaker. The C-1 circuit is connected to the NORTH bus; the C-2, C-3, and C-4 circuits can be routed to each bus via switches S-1 through S-6; The C-5 circuit can be connected to any bus through the B-5 and B-6 circuit breakers.

In extensive networks, safe and reliable high-speed bus protection is an essential element in maintaining stability and can help prevent shaft damage in the vicinity of large generating units.

The relay presented here is a high-current, low-resistance, microprocessor-based current differential relay for power supply rails.

The relay contains two separate bus differential zones in order to cover different bus sections and to initiate selective tripping actions. The relay contains a dynamic bus replica mechanism that allows buses to be protected with circuitry that can be interconnected between different sections, but with individual current measuring points.

As explained in the "Theory of Operation" section, the relay employs a dual bend point differential characteristic with double stop, with the restraint signal being generated as the maximum among the sizes of circuit connected to the protected bus.

The low-resistance working principle is through the use of the saturation detector and a current direction principle improved.

Title:Basics and protection applications of low-resistance bus differential relays - GE
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Principles and applications of low-resistance bus differential relays