4. Application
RET615 provides main protection for two-winding
power transformers and power generator-
transformer blocks. As of now, there are eight
standard configurations offering comprehensive
protection functions for detection and elimination
of operational disturbance conditions and power
transformer faults.
The standard configurations A, C, E and G are
intended for power transformers with earthed HV-
side neutrals. The A and E configuration features
low impedance REF protection while the C and G
configuration offers high impedance REF
protection. The B, D, F and H configurations fit
transformers with solidly-earthed LV-side neutral
or the LV side with a neutral earthing resistor. The
B, D, F and H configurations also fit applications
including a separate earthing transformer located
within the area of protection. The A, B , E, and F
configurations also suit applications, where the
turns ratio of the CT of the neutral earthing circuit
differs from the turns ratio of the line CTs. The C,
D, G and H configurations require that the turns
ratios of the CTs are equal.
Standard configurations E, F, G and H include
phase-voltage protection and measurement
functions which provide two-stage power
transformer overvoltage and undervoltage
protection and/or supervision.
The optional RTD/mA module offered for the
standard configurations A-D allow up to eight
analog signals to be measured via the six RTD
inputs and the two mA inputs using transducers.
The RTD and mA inputs can be used for
measuring the oil temperature at the bottom and
top of the transformer. Furthermore, the RTD/mA
inputs can be used for measuring the ambient air
temperature. The RTD inputs also offer thermal
protection of dry-type power transformers fitted
with Pt-100 temperature sensors. Temperature
measurement over the RTD/mA inputs extends
the function of the three-phase thermal overload
protection of the IED. Further, one of the RTD
inputs can also be used as a direct resistance
measuring input for position information of the on-
load tap changer. Alternatively, the tap changer
position indication can be obtained via a mA-
transducer. The analog temperature or tap
changer position values can, if required, be sent
using analog horizontal GOOSE messaging to
other IEDs. Analog values can also, vice versa, be
received from other IEDs over the station bus,
thus improving the extent of relevant information.
Transformer Protection and Control
1MRS756891 F
RET615
Product version: 4.0
16
ABB
Summary of Contents for RET615
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