Sel 411L - Table 3.31 Transformer Winding Compensation Matrices

P.3.83
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Differential Elements
resulting in the same or potentially different values of these settings. Also, the
transformer windings impacting the values of these settings may be located in
the same or a remote substation.
Normally, all CTs are connected in wye, allowing simple selection of the
compensation matrix setting. Apply special care when selecting the
compensation matrix if the CTs are connected in delta or double delta as it
may be the case in some retrofit applications. It is beneficial to re-connect the
CTs to wye in order to facilitate other applications and metering of the
currents in the relay while allowing the 87L function to compensate for the
vector group internally.
Consider the example shown in Figure 3.44. Both the W and X current
terminals of Relay 1 are associated with the wye-connected winding of the
transformer resulting in the same values of the two settings 87CTCWL =1 and
87CTCXL = 1 (assume compensation Matrix 1 is appropriate for the wye-
connected winding in this example). Both the W and X current terminals of
Relay 2 are associated with the same wye-connected winding yielding
87CTCWL = 1 and 87CTCXL = 1. Relay 3 terminal has its W current input
associated with the delta-connected winding. Assuming compensation matrix
0 is the correct matrix for this winding, you should set 87CTCWL = 0 at the
third relay.
Table 3.31 lists all transformer winding compensation matrices allowed in the
relay. Select the appropriate matrix following the principles of transformer
differential protection to compensate for the vector group and to remove the
zero-sequence currents.
Table 3.31 Transformer Winding Compensation Matrices (Sheet 1 of 2)
87CTCnL
Setting
Compensation Matrix Typical Application
0 Delta-connected transformer winding, wye virtual CT connection
1 Wye-connected transformer winding, virtual delta CT connection
2 Zigzag-connected transformer winding, virtual double delta CT connection
3 Wye-connected transformer winding, virtual delta CT connection
4 Zigzag-connected transformer winding, virtual double delta CT connection
5 Wye-connected transformer winding, virtual delta CT connection
1 0 0
0 1 0
0 0 1
1
3
-------
1 –1 0
0 1 –1
–1 0 1
1
3
---
1 –2 1
1 1 –2
–2 1 1
1
3
-------
0 –1 1
1 0 –1
–1 1 0
1
3
---
–1 –1 2
2 –1 –1
–1 2 –1
1
3
-------
–1 0 1
1 –1 0
0 1 –1