![]() ‘Grounding’ is hailed by many as the latest health trend, ensuring that the body remains in equilibrium to promote proper function, and it’s vital we adopt the same approach when it comes to protecting power supply. The NET and NER are combined in a single enclosure with excellent temperature tolerances to ensure continued operation even after a large fault current occurs. This helps them to better plan maintenance and enhance system availability, which in turn reduces downtime and ensures a consistent power output.Ĭressall produces systems that include dry type NETs and resistors to suit a variety of applications, which have power ratings ranging from ten seconds to continuous. They are found at all generating stations, electrical substations and in power distribution networks.īy continuously measuring and monitoring the operations of the power system, the CT allows operators to identify any small changes in voltage, current or function. ![]() The CT is responsible for providing a ratioed signal, scaling the large values of voltage or current present in the system down to protective measuring instruments that can be easily read. Since faults flow through the NER, a type of instrument transformer known as a current transformer (CT) can be placed before the resistor to allow instruments to monitor any changes. NETs also facilitate monitoring of electrical system operations. This ensures that any protective relaying equipment remains operational, while also preventing thermal damage to the system’s components. The NER absorbs any fault currents and safely dissipates them as heat. However, for optimum safety the transformer should be used in conjunction with a neutral earthing resistor (NER) - this adds resistance to the circuit to limit the fault current to a known level.Ī NER is placed in the neutral line of the NET so that, in the event of a fault, excessively high currents do not travel down the neutral line. A grounded system is significantly safer than an ungrounded system. NETs create an artificial neutral through one of two possible configurations: a zig-zag connection or a star-delta arrangement.Īlthough these configurations are different, they perform the same function - to provide a neutral point from which the electrical system can be grounded. Using the earth gives a way to add protective current transformers and relay to the system to detect earth fault current to open upstream circuit breakers, which can be used to clear any potential faults without negatively impacting operations. The primary function of an NET is to provide a neutral, and from this a single electrical line linked to earth. So, how does an NET mitigate these risks? Preventing problems In a worst-case scenario, this could result in dangerous transient overvoltages and extreme damage to equipment. Without a neutral, an electrical system remains ungrounded, which risks destabilising the entire system if subjected to an earth fault.
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