Basics & General
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…
Info Letter No. 20: Capacitance of conductors
In the conductors of electrical power supplies, a distinction is made between the operating capacitance…
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…
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…
Info Letter No. 8: Apparent power and reactive power in three-phase networks
The range of electromechanical and electronic measuring devices in analog – and digital technology…
Info Letter No. 5: Zero sequence voltage in three-phase networks
With balanced network operation and inequality of the impedances in the consumer circuit, the phase…
Info Letter No. 4: Summation of Alternating Currents
For the parallel connection of power sources, the principle of superposition applies, when all resources…
Info Letter No. 2: Measurement Transformers in three-phase networks (Part 2)
In a symmetrically loaded three-wire three-phase network, a two-pole insulated voltage transformer…
Info Letter No. 1: Measurement Transformers in three-phase networks (Part 1)
The direct connection of measuring devices into the network is limited for safety reasons to values…
Power Quality
Information Letter No. 24: Integration guide for the metering of a power plant according to the Requirements for Generators (2016/631) RfG
Integration guide for the measurement of a power plant (EZA) according to VDE-AR 4110 and VDE-AR 4120.
Info Letter No. 23: Direction of harmonics Sources of harmonics in the power system
Le sens du flux de puissance des harmoniques est déterminé par le signe de la puissance activ
Info Letter No. 22: Definition of power measurements according to the standards DIN 40110-2 and IEEE 1459
There is a wide range of electronic measuring devices for the digital measurement of power…
Info Letter No. 19: The evaluation of power quality and detection of interference in medium voltage network
For various reasons, interest in the continuous monitoring of network quality in medium-voltage…
Voltage Regulation
Info Letter No. 16: Hot-spot temperature and service life of transformers
The failure of a transformer not only has major economic consequences for the energy supplier, it can…
Info Letter No. 13: Parallel operation of step transformers
The rule of thumb that with parallel operation of transformers the ratio of the rated outputs should not…
Info Letter No. 11: Voltage regulation with step transformers in parallel to busbars (Part 3)
Direct measurement of the circulating current is not possible with the usual measurement…
Info Letter No. 10: Voltage regulation with step transformers parallel to busbars (Part 2)
The following considerations apply to a symmetrical operation of a three-phase network, so that the…
Info Letter No. 9: Voltage regulation with step transformers in parallel to busbars (Part 1)
Within a station, the transformers are in close proximity. Therefore, the line impedances between the…
Info Letter No. 7: Load-dependent voltage change
For the regulation of the voltage ULoad at a predetermined value at the specified load point (e.g. the…
Short-Circuit and Earth Fault Indicators
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…
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…
Info Letter No. 6: Detection of transient earth faults
When there is an earth fault in a conductor, at the start of the earth fault three events occur at the…
Earth Fault Compensation
Info Letter No. 12: E-coil control: Resonance curve procedure – Location curve procedure
In “compensated networks” the current through the point of failure is minimised with the help of an…
Info Letter No. 3: The E-coil in general
The earth fault compensation coil, e-coil or also called the Petersen coil after its inventor, is connected…
