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3 achievement(s) found

Study of Transient Recovery Voltage (TRV)

The Transient Recovery Voltage (TRV) is the voltage which appears across electrical equipment shortly after a current interruption. The waveform of the recovery voltage actually depends on the circuit configuration (inductive or capacitive nature). For example, a circuit breaker should be able to interrupt a given current for any recovery voltage provided that this value does not exceed its assigned TRV value (this TRV value is specified in the 61071 IEC standards).

The replacement of a HV circuit breaker, particularly in the case of replacement of SF6 circuit breakers by vacuum ones, requires the TRV calculations to be rechecked.

It is necessary to check that the generated overvoltages respect both the insulation levels of the present network equipment and the IEC assigned values of the breaking device. If the overvoltage levels are too high, then the installation overvoltage protection equipment should be considered (for example capacitors which reduce the rising edge steepness of overvoltages, RC circuits, surge arresters...). [...]

Transformer Energisation study

When a transformer is energised, two main phenomena occur: an inrush current and a voltage drop at the primary side. The amplitudes of these two phenomena depend greatly on the remanent (or residual) magnetic flux, the transformer saturation curve and the instant of energisation. Before being commissioned, it should be checked whether the transformer is compliant or not with the local electrical grid standards.

Before the commissioning of a 40MVA power transformer on the UK electrical grid (33kV), the customer wanted to check if the transformer complies with the national standards in terms of voltage drops (« P28: Planning limits for voltage fluctuations caused by Industrial, Commercial and Domestic equipment in the United Kingdom ») during its energisation process.

If the voltage drop exceeds the limits, the transformer will not be compliant and therefore unfit to be commissioned. Mitigation devices should be installed in order to reduce the voltage. [...]

Energisation study of transformers in a wind power station

When a transformer is energised, two main phenomena occur; an inrush current and a resulting voltage drop at its primary side. The amplitudes of these two phenomena depend greatly on the remnant (or residual) magnetic flux, the transformer’s saturation curve and the instant of energisation. Before being commissioned, it should be checked whether the transformer is compliant or not with the local electrical grid standards.
For the case of the connection of a wind power station to the French RTE grid (90kV), the client wished to consider the different energisation (simultaneous or sequential energisation) strategies (at the 21kV level) of the wind turbine transformers which respect the transient voltage drop limit (5%) at the connection point. [...]

CAPSIM - 11 Boulevard de la Grande Thumine - Parc d'Ariane, Batiment E1 - 13090 Aix-en-Provence - France
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