ABB Relion 670 Series Commissioning Manual page 107

1MRK 504 165-UEN E
Navigate to Main menu/Test/Function test mode and make sure that only the PSTPDIF
function and associated trip function blocks are enabled. All other protection functions, which
may interfere with testing or tripping shall have the setting
The PSTPDIF function is self-adaptive. Thus, special measures and procedures shall be used
during testing. Off-the-shelf available test sets with associated software and their testing
routines for standard transformer differential protection will not work, in general, for this
function. They may work for special case, when the phase angle shift is zero degree (i.e. as for
Yy0 standard power transformer). However, for specific phase angle shift (e.g. tap position) of
the protected PST, which is different from zero degree, this standard routines cannot be used.
To test this function, it is strongly recommended to use a test set with six current sources and
then follow the sequence-wise testing procedure as explained for the traditional transformer
differential protection in the paper
Differential Relays published by ABB. This paper is available on the ABB website.
To prepare the function to be tested for specific phase angle shift (e.g. specific tap position)
of the protected PST, proceed as follows:
1. Make sure that the binary input STOPCOMP into PSTPDIF function has the logical value
zero.
2. Wait for five seconds and inject the rated load using the positive sequence current
systems only on both sides of the PST, which correspond to the set default
transformation ratio and phase angle shift (typically, zero degree). Instructions on
magnitude calculation and phase angles for the six currents to be injected are available in
the above mentioned paper. When currents are injected correctly, check that all three
differential currents are approximately 0% and the bias current is 100%. These values are
available as outputs and service values from the PSTPDIF function.
3. Slowly (for example, one degree per second) rotate the positive sequence currents (i.e. all
three phases together) for winding two side until the required phase angle shift is
achieved. Note that the rotation in anti-clock-wise direction of winding two positive
sequence current will result in corresponding but negative value of the estimated phase
angle shift displayed on the IED. When PST is of an asymmetrical design, the magnitudes
of the currents on the winding two side shall also be adjusted accordingly. Once the
desired tap is reached, make sure that all three differential currents are still
approximately 0% and the bias current is still 100%. Also, check that DIFRATIO and
DIFANGLE outputs have value that corresponds to the PST tap position at which the
function needs to be tested.
4. Apply the logical value one to the binary input STOPCOMP into PSTPDIF function. The
function will now remember the transformation ratio and phase angle shift, which
corresponds to this particular PST tap. These two values will be stored and used as long
as the input STOPCOMP has a logical value one. To perform this, the IED shall be
configured accordingly beforehand. Typically, one front LHMI key or one binary input can
be configured in the configuration tool to perform this task. If additional security is
needed, this action can be only allowed when the IED is in Testmode.
5. Interrupt all six currents from the test set and verify that DIFRATIO and DIFANGLE
outputs still have value that corresponds to the PST tap position, at which the function
needs to be tested.
The function is now prepared to be tested at this particular tap position in a similar way
as the standard transformer differential protection.
The following sections explain how the PSTPDIF shall be tested for this particular tap position.
Note that, the above procedure and the following tests shall be repeated for every PST tap
position, at which the function needs to be tested.
Note that the following tests can be used for any dedicated tap-position available in the
protected PST. In actual installation, perform these tests for two extrema tap positions, mid-
tap position and one or two more freely selected tap-position(s).
Transformer protection RET670
Commissioning manual
Easy and Intuitive Method for Testing Transformer
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Testing functionality by secondary injection
Blocked set to Yes .
Section 11
101