load calculations 3 phase 4 wire 220/380 , all loads single phase

[farang]

We are being asked to preform "load calculations more and more on existing properties.
in 95% of the cases the supply is 3 phase 220/380 v, but all loads are single phase.
Grounding is most of the time either bad or non existent.
The neutral is almost never bonded to the ground.
We do install 2 meter 5/8 ground rods and merger the connection.
WE do bond the neutral to the ground at the entrance panel.
In many cases there is no ground bar in the panel (panel/distribution) box locally built with bus bars, with the load side distributed to a 3 phase sub-panel.
When we take on or inspect a project we attempt to balance the loads in the sub-panels.
I am looking for a way to make a realistic load calculation for the customer.
These load calculations are usually used to determine if the local/onsite transformer and underground wiring are adequate to add additional loads or if a new larger transformer is required.
I realize this expiation is very basic, but things here are very basic and usually don't follow "Accepted Engineering Practices"
We try and follow NEC and British codes when possible, as you can imagine we must be creative and logical in many cases.
Our primary goal is that whet we do or recommend "IS SAFE" and we will not do anything to compromise safety of either the customer or our technicians.

I am looking for help and advice from you.
I have been associated with forums in the past, we have what we have and no we do not the luxury of "getting a qualified person"
Advice and help is what I need at times. That's what I am looking for. We are not able to follow the codes or rules many times, so we do what we can to "make it safe"

One more question, How do I protect against a HOT neutral

I am an older Engineer and try to keep up with the latest codes, rules, ect. But we do not have either the parts or technology to impliment most of them, not to mention the cost and availability here.

Thanks for your help and understanding.

Farang

 

[kingpb]

My assumption here is that this is not residential for the following reasons; it is a 3ph service, and you are talking about adding loads. For those reasons, I would attempt to do the following (some suggestions may not be viable for your location):

1. Get load data for the service by hooking up a meter and/or getting billing data.
2. Gather load information about each load connected to each circuit in the panel, essentially build a consumer load list.
3. Determine connected load versus operating load, and assign a worst case diversity to each. This may mean looking at how or when each consumer operates; i.e. by process, or by time of year, or both. Worst case would be they are all on, all the time.
4. Build panel schedule assigning consumers to phases (using KVA NOT amps) by worst case loading, i.e. max.
5. Take the highest operating KVA phase, multiply by 3 and see what the minimum transformer size is needed, and check it against what is installed.
6. Make changes appropriately.

What is described is the most time consuming and intensive but will result in a highly accurate result.

On the other hand, given limited information, and or resources you can simply:
1. Measure the current on each circuit and on each phase based on the time of day when the facility is operating at it's peak. 2. Build a panel schedule based on what is existing, do appropriate conversion from amps to KVA.
3. Take the highest phase KVA, multiply by 3, and compare to what is installed. It will give you an indication of whether transformer and cable is sized appropriately or changes are needed.
4. Make changes appropriately.

As far as HOT neutral, you will need to define a little what you mean by that as that could mean different things to different people.

 

[farang]

How they meter power on a project

How they meter power on a project

All the loads are residential, here when they build a house, especially on a "project" the houses are/have 3 phase breaker panels. Wht, many strange explantions but this is what happens here. in the particular project I am working on there is a 230kva 33kv/220/380 transformer, since the "rules are 1 meter per property/title deed and the power company will not run supply underground. The project owner runs the UG cabeling from a MDB where each house is connected to a 3 phase 45/100 Amp mitsubishi meter and from the meter to the house. The problem is a new house was built and there house uses an average of 3 X what the other houses do. Most of the load is A/C's and lighting, lots of exterior and garden lights. The individual meter are read monthly and the readings totaled and the user is charged baised the total Kw divider by the total invoice than they are charged baised on the resulting price per KW. Over the last year the bill has averaged around $ 1,100 in the 2 months that the new has beed connected the KW usage has gone up maybe 10%, but the bill has almost doubled. The only thing I can think of is KW Demand, The main meter is a GE Kv Fitzall Program 16 635 924, . i am looking at the option of installing digital demand meters on each house. it is not fare to people who conserve energy, use energy saving devices to pay for the usage of some one who uses so much power and basicly doesn't care. Thanks for listening to my rant, I have come up with a KW usage table, the more you use the more you pay, still not acurate but better than everyone paying for the high power users. Any comments or advice is apperciated. Farang