Functions
2.30 100-%-Stator Earth Fault Protection with 3rd Harmonics (ANSI 27/59TN 3rd Harm.)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
219
2.30.2 Setting Notes
General
The 100 % stator earth fault protection is only effective and available if address 152 SEF 3rd HARM. =
Enabled is set during configuration. If the function is not required Disabled is set. Address 5201 SEF 3rd
HARM. serves to switch the function ON or OFF or to block only the trip command (Block relay).
Connection Type
Depending on the system conditions, at address 223 UE CONNECTION the user specified during the project
configuration if the displacement voltage U
en
is tapped via a neutral transformer (neutr. transf.) or via the
broken delta winding of an earthing transformer (broken delta) and fed to the protection device. If it is not
possible to make the displacement voltage available to the protection device as a measured quantity, computed
quantities are used and Not connected or Uen-winding must be set. The option any VT is selected if the
voltage input of the 7UM62 is to be used for measuring any other voltage instead of for earth fault protection.
With this setting the 100% stator earth fault protection function is ineffective. The option Rotor is selected if
the displacement voltage for rotor earth fault connection shall be fed in at this input. In this case, too, the 100%
stator earth fault protection function is ineffective.
The option Load. resistor is selected for 100% stator earth fault protection with 20 Hz bias voltage. With
this setting the 100% stator earth fault protection function with 3rd harmonic is blocked.
Pickup Value for 3rd Harmonic
Depending on the selection of the connection type, only one of the two setting parameters 5202 or 5203 is
accessible.
The setting values can only be determined within the framework of a primary test. The following applies in gen-
eral:
• The undervoltage stage, address 5202 U0 3.HARM<, is relevant for a connection to a transformer in the
starpoint. The pickup value should be chosen as low as possible.
• The overvoltage stage, address 5203 U0 3.HARM>, is relevant for a connection via the broken delta winding
of an earthing transformer and for a not-connected, but internally calculated displacement voltage.
As mentioned in the Functional Description in Section 2.30, side title „Broken Delta Winding“, the sensitivity of
the U0 3.HARM> stage can be increased if a power-dependent correction of the pickup value is made. The
relevant parameter for this is set at address 5207 U0 3.H.(V/100%). The default setting of this parameter
is 0, which means that the correction is disabled.
The correction setting is made with the following method:
• Measurement of the 3rd harmonic for different active powers using the operational measured values. For
the settings secondary values are recommended.
• Please note that the percentages of the active power operational measured values relate to the protected
object (S
N Gen
). These measured power values must be converted into nominal device values (see below
example).
• Interpolation of the measured values by a straight line. Reading the 3rd harmonic voltage at 100 % S
Ndevice
(P1) and 50 % S
N device
(P2) of the active power. Calculation of the difference based on the following rela-
tionship:
Figure 2-95shows an example of the measurements made on a generator. The active power dependence of
the 3rd harmonic has been determined for operation both in underexcitation and in overexcitation conditions.
To Next Page
Loading...
Need help?
General
