41-076G Relays in Type FT -11, FT-21 FT-22,FT-31, FT-32, FT-41, FT-42 Cases

Figure 1 .Current Test Plug in Testing Positions

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(Enlarged view)

Figure 2 .Short Circuiting Switch

Figure 3 .Current Test Plug in Testing Positions

Figure 4. Chassis Operated Short Circuiting Switch

Relays in Type FT -11, FT-21 FT-22, 41-076GFT-31, FT-32, FT-41, FT-42 Cases

2.0 ELECTRICAL CIRCUITSEach terminal in the case connects through a testswitch to the relay units in the chassis as shown onthe internal schematic diagrams. The relay terminalsare identified by numbers marked on the outside ofthe case. The test switch positions are identified bynumbers marked on the molded blocks.

The potential and control circuits through the relayare disconnected from the external circuit by openingthe associated test switches. Opening the currenttest switch short-circuits the current transformer sec-ondary and disconnects one side of the relay coil butleaves the other side of the coil connected to theexternal circuit through the current test jack jaws.This circuit can be isolated by inserting the currenttest plug (without external connections), or by insert-ing the ten circuit test plug. Both switches of the cur-rent test switch pair must be open when using thecurrent test plug in this manner to short-circuit thecurrent transformer secondary.

3.0 TESTINGThe relays can be tested (1) in service, (2) in thecase but with the external circuits isolated or (3) outof the case as follows:

(1) Testing in Service

The current test plug can be inserted in the currenttest jaws after opening the knife-blade switch tocheck the current through the relay, as shown in fig-ure 1. This plug consists of two conducting stripsseparate by an insulating strip. The ammeter is con-nected to these strips by terminal screws and theleads are carried out through holes in the back of theinsulated handle.

Voltages between the potential circuits can be mea-sured conveniently by clamping #2 clip leads on theprojecting clip lead lug on the contact jaw.

(2) Testing in Case

With all blades in the full open position, the ten circuittest plug (figure 5) can be inserted into the contactjaws. This connects the relay units to a set of bindingposts and completely isolates the relay circuits fromthe external connections by means of an insulatingbarrier on the plug. The external circuits are con-nected to these binding posts. The plug is inserted inthe bottom test jaws with the binding posts up and inthe top test switch jaws with the binding posts down.

The external test circuits may be made to the relayunits by #2 test clip leads instead of the test plug.When connecting an external test circuit to the cur-rent elements using clip leads, care should be takento see that the current test jack jaws are open so thatthe relay is completely isolated from the external cir-cuits. Suggested means for isolating this circuit areoutlined above, under “Electrical Circuits”.

(3) Testing out of Case

With the chassis removed from the case, relay unitsmay be tested by using the ten circuit test plug or by#2 test clip leads as described above. Any criticalfactory calibration is made with the chassis in thecase and removing the chassis from the case maychange the calibration values of these relays.

An internal schematic is available for each individualrelay showing the schematic internal wiring. The out-lines of the various cases are shown in figures 5 to11.

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Relays in Type FT -11, FT-21 FT-22, 41-076GFT-31, FT-32, FT-41, FT-42 Cases

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ABB Inc.4300 Coral Ridge DriveCoral Springs, Florida 33065Telephone: +1 954-752-6700Fax: +1 954-345-5329www.abb.com/substation automation

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