These substations are a source of temporary electrical supply and its maintenance is very easy. These substations are having high-voltage bearable wires and conductors having one neutral to ground and 4 live wires.
The secondary substations are lined alongside secondary transmission lines adjacent to loads. The primary grid substations are linked with bulk load centers alongside primary lines of transmissions. The step-down substations are linked with load centers as there is a requirement of different voltage levels for various loads.
Hence, these voltages are needed to be stepped-up for economical transmission of electrical energy over greater distance. The step-up substations are linked to generating stations directly as generation is achieved in lower voltages. Substation Types based on Operating Voltage Levels.
^ A few manufacturers now offer a single-bottle vacuum breaker rated up to 72.5 kV and even 145 kV. See -/full-knowledge-about-integrated permanent dead link Electrical Engineering in India, vol 157 issue 4 pages 13-23. “Chapter 1”. Power Circuit Breaker Theory and Design (Second ed.). IET ISBN. These are used on overhead electric power distribution systems, to prevent short duration faults from causing sustained outages.
Recloser — A type of circuit breaker that closes automatically after a delay. Earth leakage circuit breaker (ELCB) — This detects current in the earth wire directly rather than detecting imbalance. Residual current breaker with over-current protection (RCBO) — combines the functions of an RCD and an MCB in one package.
Several firms have looked at adding monitoring for appliances via electronics or using a digital circuit breaker to monitor the breakers remotely. This increases the availability , since open-air disconnecting switch main contacts need maintenance every 2-6 years, while modern circuit breakers have maintenance intervals of 15 years. The disconnecting circuit breaker (DCB) was introduced in 2000 14 and is a high-voltage circuit breaker modeled after the SF6-breaker.
Circuit breakers can be classified as live tank, where the enclosure that contains the breaking mechanism is at line potential, or dead tank with the enclosure at earth potential. Vacuum circuit breakers have longer life expectancy between overhaul than do other circuit breakers. These are generally applied for voltages up to about 40,500 V, 10 which corresponds roughly to the medium-voltage range of power systems.
To provide simultaneous breaking on multiple circuits from a fault on any one, circuit breakers may be made as a ganged assembly. A magnetic-hydraulic circuit breaker uses a solenoid coil to provide operating force to open the contacts. This allows short current spikes such as are produced when a motor or other non-resistive load is switched on. With very large over-currents during a short-circuit, the magnetic element trips the circuit breaker with no intentional additional delay.
The thermal portion of the circuit breaker provides a time response feature, that trips the circuit breaker sooner for larger over currents but allows smaller overloads to persist for a longer time. They are the most commonly used circuit breakers in the USA. As the current in the solenoid increases beyond the rating of the circuit breaker, the solenoid’s pull releases the latch, which lets the contacts open by spring action.