POWER FACTOR REGULATOR
The power factor regulators (hereinafter referred to as “regulator”) shall be micro-processor based, solid state in construction, compact, easy to install and use. The regulator shall automatically and/or manually step-in or step-out various capacitors to correct the power factor to the required pre-set level.
The regulator shall be insensitive to harmonics and screened from stray electric and magnetic interference and shall be housed in case suitable for panel mounting. Operating ambient temperature shall be up to 60 0C. The regulator shall be 6 or 12 steps type as specified in the Drawing and/or Bill of Quantities. No-voltage trip and zero current trip shall be provided.
For a voltage loss of longer than 15 ms or current loss of longer than 3 s, all capacitor stages connected shall be switched off. until discharged. After voltage or current is restored the regulator switches the required steps on.
4.2 SWITCHING SEQUENCE
The regulator shall incorporate minimum following automatic switching sequence modes, viz. cyclic switching sequence and multi-step switching sequence allowing minimum following combinations of switching programme of capacitor stages:
(a) 1:1:1:1:1:1 … (b) 1:1:2:2:2:2 …
(c) 1:1:2:2:4:4 … (d) 1:2:2:2:2:2 …
(e) 1:2:4:4:4:4 … (f) 1:2:4:8:8:8 …
The first three control output may be allowed to be set as fixed steps which are not included in the normal control cycle but are switched on immediately after the regulator is switched on and always remain switched on.
4.3 SETTING AND DISPLAY
The following settings and displays shall be incorporated :-
(a) Continuous digital actual power factor display (0.00 inductive – 1.00 – 0.00 capacitive);
(b) Capacitor step indication;
(c) C/k inductive setting and display;
(d) C/k capacitive setting and display;
(e) Target power factor setting and display (0.80 inductive – 1.00 – 0.80 capacitive);
(f) Operation delay setting and display (5 s to 300 s);
(g) Apparent current display or Active/Reactive current displays;
(h) Flashing display when alarm is activated.
If specified in the Drawing and/or Bill of Quantities, the following setting and display shall be incorporated in addition to the above :-
(a) Harmonics content display (5th, 7th and 11th harmonics on voltage);
Provision of following alarm shall be incorporated :-
(a) Power factor alarm : If the threshold values set for ‘switch-on’ and ‘switch-off’ are exceeded and no further change can take place in the output steps, the alarm signal functions.If specified in the Drawing and/or Bill of Quantities, the following alarms shall be incorporated in addition to the above :-
(a) Harmonic Alarm : When the harmonics threshold values are exceeded, the alarm goes off; and
(b) Over-current alarm : If the capacitor current exceeded the rated current set, the alarm goes off.
4.5 MODE OF OPERATION
When the regulator is in manual operation mode, the capacitor steps can be switched in step by step and switched out in reverse step by step manually. The step that is being switched on shall be displayed. With the regulator in OFF mode, all equipment shall be switched off and deenergised.
In the automatic mode, the regulator shall switched in or switched out the required capacitors without undue switching on and switching off at any particular step to reach the nominal target power factor. In any event the zero voltage release function must take precedent at all modes of
operation to prevent capacitive current surge.