HU or HU-1 Testing Notes
General Polar Unit Pickup Notes.
Wdg #1 Tap is the top row of taps. Current in on term #5 & out on term #3.
HU only; Wdg #2 Tap is the bottom row of taps. Current in on term #7 & out on term #3.
HU-1 only; Wdg #2 Tap is the middle row of taps. Current in on term #7 & out on term #3.
HU-1 only; Wdg #3 Tap is the bottom row of taps. Current in on term #9 & out on term #3.
Always test the pickup value of the polar units as a first test and a last test. This is so you know the condition & proper tap values going in to testing and finishing testing of the polar units. You sometimes need to polarize the polar units for proper operation of the relay and some of these tests actually changes the polarization in a noticeable way. Pickup tests does not and gives you a way to notice this. As left P.U. does not equal has found and you did not change calibration for example. As found P.U. does not fall within specs for another. SOMETIMES ALL YOU HAVE TO DO IS POLARIZE THE POLAR UNITS. Polarize with wdg #1 on the 2.9 amp tap. This is to keep the current magnitude to a reasonable value.
AFTER POLARIZING ALWAYS PERFORM P.U. & D.O. 2 or 3 TIMES ON THE FIRST WINDING TO ASSURE CONSISTENT RESULTS. THE FIRST ONE OR TWO P.U. TESTS ARE ALWAYS HIGH.
THE UPPER POLAR UNIT IS THE HARMONIC RESTRAINT POLAR UNIT AND SHALL NEVER BE RE-CALIBRATED FOR CHANGING THE SLOPE FROM 30% TO 35%.
P.U. WILL ALWAYS BE .3 * wdg_tap_value PLUS OR MINUS 10 PERCENT.
THE LOWER POLAR UNIT IS THE DIFFERENTIAL POLAR UNIT.
P.U. IS PLUS OR MINUS 10 PERCENT OF .3 * wdg_tap_value for a 30% slope relay.
P.U. IS PLUS OR MINUS 10 PERCENT OF .35 * wdg_tap_value for a 35% slope relay.
D.O. SHOULD BE GREATER THAN 47.5% of P.U. TO ASSURE GOOD TOGGLE OF THE POLAR UNIT WHICH IS ESSENTIAL FOR PROPER POLAR UNIT OPERATION.
General Harmonic Restraint Testing Notes.
ALWAYS USE .212 * wdg tap value FOR AMOUNT OF PURE 2nd HARM CURRENT (I2nd). This is the correct amount of I2nd determined by a fourier analysis of pure 2nd harmonic when applying .8 * wdg tap value through a diode as in the I.L. testing method.
This method of testing duplicates the half wave method described in the I.L. and gives consistent results across the taps.
TOLERANCE IS 14% to 17% second harmonic restraint. Below that you operate.
%second harmonic=( I2nd*1.2267/sgrt (Ifund^2 + I2nd^2))*100.
When using the half wave method described in the I.L. the tolerance was still 14% to 17% second harmonic restraint. Using .8*wdg tap value for the amount of half wave current applied. This value is called Idc and uses this relationship ;
%second harmonic= 47*Idc/( Ifund + 1.11*Idc ) .
THE HRU POLAR UNIT P.U. HAS TO BE WITHIN TOLERANCE FOR THE HARMONIC RESTRAINT TEST TO BE WITHIN TOLERANCE.
General Slope Testing Notes.
Slope Test like the I.L. (41-347.1S), Table 1 for an HU and Table 2 for an HU-1
Slope test all possible winding combinations to test all the circuitry.
Through Current goes in the wdg with the lesser tap value and out the wdg with the larger tap value. Diff Curr goes in terminal #3 and out the larger tap value wdg.
The following relationship gets you close to expected value but its only close and so follow the table in the I.L.
%SLOPE = [T1/T2 ( Idiff/Ithru + 1) -1] * 100
T1 = smaller restraint winding tap value.
T2 = larger restraint winding tap value.
Idiff = [ ( %SLOPE/100 + 1) * Ithru * ( T2/T1) ] - Ithru
Instantaneous Notes.
Perform the Instantaneous Test using wdg #1 on the 2.9 amp tap. This is so there isn’t as much change to the polar unit characteristics during Instantaneous Testing.
Polarize and then do an as-left Polar Unit P.U. Test of all the wdgs after performing the Instantaneous Test (and, or) the Slope Test.
TOLERANCE IS PLUS OR MINUS 5 PERCENT OF 10 * wdg_tap_value.
Target & Seal-In Notes.
Test that this unit picks up on DC Current.
2 amp or the .2 amp tap