Lagging and Leading Power Factors

How in blue blazes did you get a leading pf?

TVP45,

I don't know how the OP got a leading power factor, but, leading power factor is a real issue for data centres and what it does to the UPSs that are supposed to be protecting them.

This is caused by all the Switch Mode Power Supplies, usually multiples of two per server.

With all the capacitors and switching, there is usually more leading than lagging and the harmonics can get nasty if not managed properly.

We actually had to put in a PFC to generate a lag PF for when the UPSs are switched to by-passs for maintenance.

For the OP, leading PF is just as bad if not worse that a badly lagging PF due to the effects of Harmonics and while I don't know Malaysia's codes I would expect that the power suppliers would not be happy about that much of a leading PF.

Regards,
Sapper.

Wow! I can see how you get leading pf, but I wouldn't have thought anyone would tolerate that long, except during switching operations when you can't help it. That must tear the &^^%$ out of the electronics??

Laging power factor will penalty and normaly leading power factor there is no penality beacuse, due to laging power factor the efficiency of all the switch gears( starting from cables ,transformers,switch gears and the transmission line) efficiency goes down. and due to laging power PF low voltage also occures hence current also increases in the whole system. But due to leading power factor the same problems are not happens but. where there is own power House, the performance of Automatic Voltage Regulator (AVR of TG) is decreased or there may be nucence tripping occured.

Normally in long transmission line with no load/ or lesser load there is a leading in power factor. but it never happens any problem.

the question is, if my power factor is 0.5 leading (capacitive), is it good or bad? or will get penalty? my country is in Malaysia.

That doesn't sound right at all. What sort of large capacitive loads are you running to get such a large (and rare) leading power factor?

Is this a hypothetical question or have you actually measured this on your site?

You haven't just oversized your site's power factor correction capacitor banks (or left them switched on when your site loads are off) have you?

Please provide more details as electricity penalty costs due to this excessively large leading power factor may be the least of your sites potential (and expensive) problems.

leading power factor too is not good for power system's health, because at low loads and leading power factor the flow of power reverseses and reciving end voltage become more than rated voltage.

Si try to keep it within .90 to .95

The answer to regcan80's question depends on what is creating the leading power factor. In the US, some utilities will pay large customers to overexcite their synchronous motors & provide a leading power factor. This helps the utility by reducing the need for power factor correction on a large industrial circuit.

However, if a customer consistently generates a leading pf without arrangement with the utility, he may get disconnected for violating the terms of service. That is because, on more lightly loaded circuits, a leading power factor will result in a higher voltage near the source of the leading pf than that supplied by the substation. It can cause overvoltage problems in your own equipment, as well as other customers on the same feeder.

Sapper has a good point. A leading pf created by switch-mode power supplies creates some really ugly harmonics, which can and will damage electronic equipment such as PLC's, computers, televisions, generator controls, etc. The harmonics can also affect the ability of switches & circuit breakers to interrupt current, because a higher frequency arc tends to sustain itself better than a power frequency arc.