ABB GFD233A static excitation system 3BHE022294R0101 electrical products

Description

• GFD233A Differential current: < 0.03 × CT as the two winding currents are equal once

correctly transformed inside the relay.

• The loading of each winding would be 100% of rated.

The above results can be GFD233A verified with two adjustable sources of three-phase current. With

a single current source, how the relay performs the necessary phase angle corrections

must be taken into account. Table 5–1: Transformer types on page 5–13 shows that the Y

side currents are shifted by 30° to match the Delta secondary side. The 30° phase shift is

obtained from the equations below:

(EQ 7.7)

By injecting a current into Phase A of Winding 1 and Phase A of Winding 2 only, I W1b = I W1c

= 0 A. Therefore, if we assume an injected current of 1 × CT, the transformed Y-side currents

will be:

(EQ 7.8)

For the purposes of the differential elements only, the transformation has reduced the

current to 0.57 times its original value into Phase A, and created an apparent current into

Phase B, for the described injection condition. If a 1 × CT is now injected into Winding 1

Phase A, the following values for the differential GFD233A currents for all three phases should be

obtained:

Phase A differential: 0.57 × CT ∠0° Lag

Phase B differential: 0.57 × CT ∠180° Lag

Phase C: 0 × CT.

7.4.4.3 Effects of Zero-sequence Compensation Removal

Note

The transformation used to obtain the 30° phase shift on the Y-side automatically

removes the zero-sequence current from those signals. The 745 always removes the

zero-sequence current from the delta winding currents.

If the zero-sequence component is removed from the Delta-side winding currents, the

Winding 2 current values will change under unbalanced conditions. Consider the case

described above, with the 1 × CT injected into Phase A of Winding 2.

For the 1 × CT current, the zero-sequence value is 1/3 of 1.0 × CT or 0.333 × CT A. The value

for I W2a’ is therefore (1.0 – 0.333) × CT = 0.6667 × CT A. This value must be divided by the CT

error correction factor of 0.797 as described above.

Therefore, the value of differential current for GFD233A Phase A, when injecting 1 × CT in Winding 2

only, is:

(EQ 7.9)

The action of removing the zero-sequence current results in a current equal to the zero

sequence value introduced into phases B and C. Hence, the differential current for these

two elements is

Now, applying 1 × CT into Winding 1 Phase A and the same current into Phase A Winding 2,

but 180° out-of- phase to properly represent CT connections, the total differential current

in the Phase A element will be (0.57 – 0.84) × CT = –0.26 × CT. The injection of currents into

Phase A of Windings 1 and 2 in this manner introduces a differential current of (–0.57 × CT

+ 0.42 × CT) = –0.15 × CT into Phase B and (0.0 × CT + 0.42 × CT) = 0.42 × CT into Phase C.

Details: If you need urgent delivery orders, please feel free to contact us, and we will try our best to meet your needs.
Price problem: If you find that other suppliers offer cheaper prices for the same product, we are also willing to provide you with reference prices and give you further discounts.
Contact us:+86 180 6092 3929
Mail: 2235954483@qq.com
Contact: Chen