Save 50% on all EEP Academy courses with Enterprise Membership Plan and study specialized LV/MV/HV technical articles & guides.

# Industrial switching & protection systems (Application guide)

Home / Download Center / Electrical Engineering Books and Technical Guides / Electrical engineering guides / Industrial switching & protection systems (Application guide)

## Short circuit currents

A short circuit current is a current triggered by a negligible impedance fault between points of an installation normally having a potential difference.

3 levels of short circuit currents can be identified:

1. Peak short-circuit current (Isc peak) corresponds to the top of the current wave, generating heightened electrodynamic forces, notably at the level of busbars and contacts or equipment connections,
2. RMS short-circuit current (Isc rms): rms value of the fault current which leads to equipment and conductor overheating, and may raise the potential difference of the electrical earth to a dangerous level,
3. Minimum short-circuit current(Isc min): rms value of the fault current establishing itself in high impedance circuits (reduced section conductor and long conductors, etc.). It is necessary to quickly eliminate this type of fault, known as impedant, by appropriate means.[/info_box]

## Harmonics

### Definition

Harmonic current or voltage are mains â€śstrayâ€ť currents or voltages. They distort the current or voltage wave and lead to the following:

• an increase in the current’s rms value,
• a current passing the neutral being higher than the phase current,
• transformer saturation,
• disturbance in low current networks,
• intemperate tripping of protection devices, etc.,
• distorted measurements (current, voltage, power, etc.).
Harmonic currents can be caused by current transformers and electric arcs (arc furnaces, welding machines, fluorescent orÂ gas-discharge lamps), but mainly by static rectifiers and converters (power electronics). Such charges are termed non-linearÂ loads.

Harmonic voltage is caused by harmonic current passing through mains and transformer impedance.

### Harmonic voltages

For a measurement period of one week and value set to 95%, the averaged 10 min harmonic voltages should not exceedÂ the values given in the following table Total voltage distortion rate should not exceed 8% (including up to conventionalÂ number 40).

 Title: Application Guide – Industrial Switching & protection Systems // SOCOMEC Format: PDF Size: 12.3 MB Pages: 124 Download: Right here | Video Courses | Membership | Download Updates

50% Discount đź’Ą - Save 50% on all 90+ video courses with Enterprise Membership plan.

1. FAzli
Apr 13, 2017

Thank you electrical engineering portal

2. Flos F. Famarin
Jun 29, 2015

Thanks to EEP group

3. Joseph Sagoe
Sep 29, 2014

Thanks to EEP groups.

4. Than Dai
Jul 28, 2013

Thank EEP forever.
regards TD