Unbalanced voltages are unequal voltage values on three-phase circuits that can exist anywhere in a power distribution system. Unbalanced voltages can cause serious problems, particularly to motors and other inductive devices. Typically these voltages may differ by a few volts or more. When voltages differ excessively, problems occur.
For general motor protection, it is always assumed that the system voltage is stable. This is due to legislation such as NRS 048. This legislation is divided into several parts, mainly guiding the quality of the power supply (QOS), focusing on voltage parameters such as magnitude and dip time.
However, during fault conditions, the system is unstable and it is essential to know the voltage variation to protect the motor comprehensively. It is generally known that in a fixed power system there is a 1% increase in current measurement, therefore a 2% increase in voltage. The sudden fluctuating voltage also contributes to deteriorating winding insulation in a motor, thus reducing the motor life. NewElec has relays such as its NewCode KE range that measure voltage to ensure comprehensive motor protection.
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