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• Measure Transients for Damage Control

Transient overvoltages occur as a result of lightning, faults in power networks or reactive loads switching, causing severe damages to equipment. According to the EN50160 standard definition, transient overvoltage is a short duration oscillatory or non-oscillatory overvoltage usually highly damped and with a duration of a few milliseconds or less. Due to the short duration of these events, they can only be detected by special, fast measurement and recording.

The Problem

Global damages due to transient overvoltages are estimated at billions of dollars annually. These disturbances cause serious damage to equipment, such as transformers, capacitors and computers, and result in financial losses for factories and business activities, as well as to customers.

Damage to Customers & Equipment Transformer explosions & fire Nuisance tripping of circuit breakers Unexplained fuse operation Loss of computer or controller memory Tripping of variable speed drives Motor overload operation Computer system data alterations Errors of microprocessor controlled equipment Damage to electronic components Failure and damage to power factor correction capacitors Causes of Transient Overvoltages Lightning Capacitor switching Line switching System faults Switching of large inductive loads (motors) DC – loads switching
Measuring Problems The duration of transient overvoltages is very short, from microseconds to 10msec, and the amplitude of the peaks is high. Standard Revenue and Power Meters are unable to measure and record these transients.
Revolutionary Device for a Smart Solution
With the new EM720T eXpertmeter™, SATEC is now able to offer a solution to the deadly problems caused by transient overvoltages. The EM720T Revenue Energy Meter is class 0.2S accuracy and has special high impedance inputs for measuring high voltages between phases and neutral relative to ground. The EM720T records four voltage waveforms simultaneously (3 phase and neutral relative to ground), in fast speed. It can also measure transient pulses with amplitude of up to 2kV and isolation withstands of voltage and current inputs relative to ground up to 6kV. The Battery Backup Power Supply (BPS) with built-in rechargeable NiMn battery provides 2.5 hours of backup, enabling to record transients at the time of the fault.

Transient Overvoltages Recorded by EM720T

Transient overvoltages are detected as impulse according to next parameters—impulse amplitude, duration and rise time. In the EM720, minimal impulse amplitude is set by the consumer. The impulse amplitude is referenced to the nominal voltage amplitude (1.414 Un), and should be set at 30% or more. The impulse duration may be from 20 microsecond up to 10 ms.

Figure 1. OMICRON Signal Generator waveforms

Figure 1 shows a waveform generated by OMICRON and recorded by EM720. The waveform has an impulse of 1 ms and an amplitude of 100%. In this experiment, voltage neutral input was connected to ground input of the EM720.

Figure 2. SATEC Signal Generator waveforms

Figure 2 shows a waveform generated by a special device.
The waveform has an impulse of 88 microsecond and an amplitude of 410%.

Figure 3. Transient overvoltage in a 400V network

The waveform in figure 3 was recorded by EM720. The instrument
was installed in a 400V network. The Impulse has a duration of 22 microseconds and an amplitude of 378.9V (phase to ground).

Figure 4. Transient overvoltage with equipment damage

Figure 4 shows amplitude in phase 1—720.4V (phase to ground).
Amplitude in neutral—369.6 (phase to ground). In the case illustrated here, damages were caused to electronic equipment.

Figure 5. Power Quality Event Log

Figure 5 lists transient overvoltage events recorded in PQ Log.