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13

ABB

Figure 8: Transformer Tap and Ratio Chart

bushing, a potential device and a burden. Therefore,
since any one of these is not a perfect duplicate of any
other of its own kind, it is necessary to completely
re-adjust when any one of the combination is changed.

Auxiliary Winding

The output winding with terminals Z1, Z2 and Z3 is
designed for a maximum of 75 watts, and no more
than this amount of burden shall be connected to the
Z terminals, even though the total rating of the device
may be in excess of 75 watts in some cases.

Operating Tap Voltage

The primary of the device transformer is designed for
continuous operation at voltages not in excess of 7600
volts. Therefore, it is necessary to check the voltage
H2-H3 after any alteration to be certain this voltage
does not exceed 172V.

Adjustment-Need For

The adjustment of a potential device is in effect a
“tuning” procedure to affect a “match” between condenser

Summary of Contents for PBA2

Page 1: ...Bushing Potential Device Type PBA2 PTAE APD903 IZUA 7711 210 Instructions for Installation and Maintenance ...

Page 2: ...tenance and all details and variations of this equipment do not purport to be covered by these instructions If further information is desired by purchaser regarding his particular installation operation or maintenance of his equipment the local ABB Inc representative should be contacted ...

Page 3: ...ction and with a grounded external shield connects the potential device to one of the metallic layers of the condenser bushing The device network see Fig 6 consists of a main transformer having adjustable reactance an auxiliary transformer of adjustable ratio a tapped capacitor to correct burden power factor a protective spark gap and a dead front adjusting panel A grounding switch permits de ener...

Page 4: ... variance with the foregoing tabulation In this connection it is to be noted that the auxiliary capacitance built into each device varies according to the device application See page 10 Calculation of Approximate Adjustment Performance The Type PBA2 Potential Device is a Class A device as defined by AIEE Standard 31 and NEMA Standards SG4 1968 The regulation characteristics with respect to varying...

Page 5: ...er is removed Discharge the bushing tap layer by touching the socket contact with a grounded wire 1 If the bushing is ABB O plus C or other type that permits addition of transformer oil to the test tap with the tap cover in place you may choose to fill the PBA connector housing with transformer oil In this case do not add the petrolatum to the PBA connector housing 2 Otherwise pack the inside of t...

Page 6: ...66 4 volts note that the ratio of these two voltages in the output is fixed so that only one of them need be adjusted and checked To check the phase angle of the output voltage requires either a phase angle meter having two voltage coils a low voltage voltmeter or an oscilloscope The oscilloscope is probably the most satisfactory for phase angle adjustment If the reference voltage being used is th...

Page 7: ...am for checking the phase angle and ratio using the oscilloscope with vertical and horizontal sweeps each energized at 115 volts 60 hertz The oscilloscope shall be adjusted so that the total deflection in each the vertical and the horizontal directions is roughly the same The reference and the output voltages are in phase when the trace on the oscilloscope is the nearest possible to a single strai...

Page 8: ...rect position of the buck boost switch and then the finer adjustments of the phase angle switches is a straight forward procedure to secure a straight line trace on the oscilloscope Start by first trying the larger steps 192 turns is the largest step and if any step is in excess of that required then drop back to the next lower turns in the same switch For example with the three rotary switches in...

Page 9: ...9 ABB Figure 5 Curve of Ohms versus Turns of Reactance ...

Page 10: ...sted device In the case of delta connected three phase burdens it is necessary to make preliminary or approximate adjustments of each device first and to then re check and trim each device one or more times until the three phase voltages to ground are equal and each in phase with its reference voltage When final adjustment is accomplished with the burden connected check voltage H2 H3 This voltage ...

Page 11: ...e actual system line to ground voltage at the condenser bushing The dial setting of the voltage adjustment should then total dial volts 173 e 44 1 3 For the phase angle adjustment it is necessary to know the capacitive reactance XC which must be series tuned This value in ohms is for 60 hertz XC 1012 377 C1 C2 C3 4 377 2 πf with f 60 hertz Using this value of XC refer to curve Fig 5 and using the ...

Page 12: ...ms for 60 hertz or 104 000 to 670 000 ohms for 50 hertz Let ex maximum permissible reactance voltage then ex 7600 2 e2 5 Max watts ex x e XC K 6 Constant K from empirical equation K 95 078XC 100 000 but not less than 11 Application Notes Heater Each device contains two vitreous enameled resistors of 1200 ohms each These are to be energized from an external source for the purpose of preventing the ...

Page 13: ...75 watts and no more than this amount of burden shall be connected to the Z terminals even though the total rating of the device may be in excess of 75 watts in some cases Operating Tap Voltage The primary of the device transformer is designed for continuous operation at voltages not in excess of 7600 volts Therefore it is necessary to check the voltage H2 H3 after any alteration to be certain thi...

Page 14: ...ay not register correctly if coils are not operated at their rated voltage or current 4 Recheck degree of power factor correction 5 Calculate the approximate adjustment in line with sections on Calculation of Approximate Adjustment and Unusual Combinations to be sure device is applicable to the combination at hand 6 Check for loose grounded or open connections within device 7 Frequency other than ...

Page 15: ...15 ABB Notes ...

Page 16: ...E AND JUDGEMENT WITH RESPECT TO BUSHINGS THIS INFORMATION SHOULD NOT BE CONSIDERED TO BE ALL INCLUSIVE OR COVERING ALL CONTINGENCIES IF FURTHER INFORMATION IS REQUIRED ABB INC SHOULD BE CONSULTED NO WARRANTIES EXPRESSED OR IMPLIED INCLUDING WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY OR WARRANTIES ARISING FROM COURSE OF DEALING OR USAGE OF TRADE ARE MADE REGARDING THE INFORMA...

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