Detection of transient earth faults

Info Letter No. 6

Three simultaneous processes

When there is an earth fault in a conductor, at the start of the earth fault three events occur at the same time.

  • The voltage U1E (phase-earth) of the conductor affected by the earth fault collapses, with a saturated earth fault U1E goes to zero
  • the zero sequence voltage UNE rises abruptly from the operating value (a few volts) to a higher value;
    with a saturated earth fault 
  • the capacitance CLE (phase-earth) of the faulty conductor is discharged while the charge state of the capacitances CLE of the two fault-free conductors is also abruptly changed (recharged) (up to ULL) by the simultaneously varying voltage U1E

Zero sequence voltage

The zero sequence voltage UNE occurs regardless of the location of the earth fault in the entire electrically connected network in nearly the same way and has the same waveform and frequency as the line voltage. The zero sequence voltage UNE is present as long as the earth fault persists.

Voltage waveform before and after an earth fault

Discharge of CLE of the earthed conductor

When there is an earth fault in a conductor, the capacitance CLE of all the lines of the electrically connected network discharge across the earth fault to earth. This process occurs only once immediately after the start of the earth fault and is completed in a short time.

The timing of this discharge current is dependent on the data of the conductor. The ratio of the ohmic resistance to the inductance of the conductor determines the properties of the resonant circuit consisting of these elements. If the inductance is relatively small, the discharge current is an aperiodic, steadily decaying DC; with larger inductance values it is a periodic decaying alternating current.

Typical patterns of the discharge current

The amplitude of this current surge is dependent on the time of occurrence of the earth fault. If this coincides with the maximum of the half-wave of ULN, the initial amplitude of the current surge also reaches the maximum and it goes to zero if the fault occurs during the zero crossover.

Need more information?

Contact us!


News from the product groups

EORSys – News

General Knowledge

The Future of the Distribution Grid: Focus on Digital Secondary Substations

In this technical report, Gerald Jacob (Product Manager "EORSys") uses a specific example to illustrate how distribution system operators can meet the challenges of energy transition in the medium and low-voltage grid with future-proof secondary substations.

Read more

General Knowledge

Earth fault explained – basics and functions of an electrical phenomenon

Everything you need to know about earth faults - from the basics, causes and examples to the consequences. Find out more in this article about earth fault clearing, compensation, location and the benefits of constant monitoring to ensure a safe power grid.

Read more

General Knowledge

Ready for the smart grid of the future?

All information about smart grids/intelligent power grids, the technology behind them, advantages, disadvantages, challenges and current distribution.

Read more

Info letter

Info Letter No. 21: The influence of the contact resistance at the earth-fault location on the zero sequence voltage UEN in compensated networks

The earth fault in compensated networks is usually presented without a contact resistance at the fault...

Read more

Info letter

Info Letter No. 18: Transient relay for high resistance, intermittent and recurrent earth faults (Part 2)

Figure 3 can also be used for the determination of static earth faults. In an isolated network the entire...

Read more

Info letter

Info Letter No. 17: Transient relay for high resistance, intermittent and recurrent earth faults (Part 1)

The statistics show that earth faults constitute a large proportion of network faults. Conventional relays...

Read more

Info letter

Info Letter No. 15: Earth fault location using the harmonic procedure (Part 2)

For the study of the behaviour of the harmonic currents and voltages in the compensated network, at...

Read more

Info letter

Info Letter No. 14: Earth fault location using the harmonic procedure (Part 1)

For the following considerations a network with three outputs and an earth fault in line 1 in output...

Read more

Special Publication

Cost Efficient Management of Digital Secondary Substations: Earth Fault Indicator EOR-3DS as Digitisation Unit for Secondary Substations

Digital secondary substations are becoming a key element for distribution system operators in terms of automation, monitoring, and efficient operations of their networks. Read this technical report about the EOR-3DS in its role as digitisation unit for secondary substations.

Read more

Contact request:

* Mandatory

Your data is being processed

a-eberle kontakt newsletter ×

Our seminars &

► Register here!