Search results for query: *

Hi all, Should the star point (neutral) of LV embedded generator that runs long term parallel with utility be directly connected to then customer's LV earth? The situation is that the customer has LV (PME) supply from utility transformer. At site customer has installed a CHP LV generator...

Hi All, I am involved in accepting connections of new generators on our LV, 11kV and 33kV distribution network. Most of new generators are either CHP (gas engine) that will run Long Term parallel with utility (or) Diesel Generators (DG) that will run parallel only for short duration (1 min...

Many thanks for your valuable comments. musa UKPN

Hi, I know that we use X1/R1 for X/R ratio in case of three phase fault. I want to know what will be the X/R ratio for single phase to ground fault? Can I use (X1+X2+X0)/(R1+R2+R0)? Regards, musa UKPN

I am sure you can get the specs from Manager M&T (Metering and Testing) of any Distribution company in Pakistan. If you are specifically interested in Islamabad area; the DISCO is called IESCO - Islamabad electric supply company Ltd. See web link...

@ prc; yes your interpretation is right. P-2/6 is the security of supply criteria in UK. It gives the guidelines for the security of supply requirements of an existing or new system. Supplies are classified as maximum demands of A<=1MW; 1<B<12MW; 12<C<60MW; 60<D<300MW; 300<E<1500MW and F>1500MW...

@ Scotty: Thanks for the comments. It is usual practice at our DNO not to parallel the LV's of the two distribution transformers that feed the a particular customer's load. Under normal running conditions; the load is divided between the two transformers and bus section or LV links between the...

Thanks all for the valuable comments. @ Marmite: Thanks for your comments. We are aware of P-2/6 requirements. However, most of developers in London are reluctant to offer enough space for putting in 1MVA substations.These developers are ready to duplicate 3MVA transformers to get the required...

Hi, Our Electric utility (in IEC world - UK) is now providing customer connections at 33kV distribution voltage. Loads equal or above 5MVA threshold will be connected directly to 33kV rather traditional 11 or 6.6kV feeders.These bulk customers are metered at 33kV. Most of the new developments...

You can buy ER P-2/6 (security of supply) from ENA website (see link below): http://www.ena-eng.org/ENA-Docs/EADocs.asp?WCI=SearchResults&DocSubjectID=109 musa UKPN

Saya88, The positions of Sectionalizers on your SLD are ok. I consider following factors while deciding number and location of the sectionalizers: 1). Length of line/ branch 2). No. of customers effected 3). The load effected by operation of sectionalizer on faults 4). the previous fault...

Does it mean that no bonding between power neutral and body grounding should exist? If so how can we bond the two? musa UKPN

If the cable connecting the transformer to MV gear is not very long, I would add no extra breaker. The protection at HV gear and the downstream LV arrangement also to be considered. I have seen many 11/0.4kV transformers connected directly to the short cables. Usually transformer rooms are...

In your situation the 1-phase breaker should be rated for 3-phase fault level. I understand that the intake supply is 3-phase. A 3-phase fault downstream of the switchboard will produce higher current than 1-phase to ground (as per you figures). musa UKPN

I have seen this before. The reasons were found to be due to faults on any of the 11kV distribution feeders from the utility 132/11kV substation, but the dips were not of the range of 3 seconds! When compared the date/ time of the dips recorded at customer's installation exactly co-related to...

Correction above: .......not advisable to connect solar dist gen... because of low fault levels......... musa UKPN

I will ask a simple question: is the undervoltage relay at motor have any time delay settings? I have seen similar tripping at an office building while the chiller motors started. what I understand that if you add a time switch and/or replace this undervoltage with a modern having time delay...

The decision regarding what should be an overload limit (for tripping)is open choice and largely depend upon the downstream connected load and its characteristics in addition to the cable ampacity. A low settings would also have its drawbacks like nuisance tripping during momentry faults; load...

I am not familiar with NEC requirements; however being working at utility I know that two alarms are usually set called high alarm and very high alarm for the MV cable rating. The high & very high limits can be slightly higher than the cable rating (we call this higher rating as cyclic rating)...

In my view it also depends on how are you burying the 3ft length? If it is in proper size duct where air can circulate; and there is less probability of the duct air passage blockage; there is no harm to use the free air ratings. However, being conservative I would personally like to de-rate it...