Transformer Fuse Sizes and Types

I am rather disturbed by the quantity of questions being asked regarding SIMPLE ELECTRICAL questions for industrial application problems that people SHOULD know when doing this sort of thing for a living.

Is this a homework question or are you really an electrician or electrical technician who doesn't know how to size a fuse for a transformer. Seriously, do you NOT know how to work out transformer current and apply fuse curves. This is elementary stuff which you MUST know if doing this sort of work.

PLEASE get a professional to do this for you.

Thanks all the same

Hello sir,

I dont think u should ans. anyone like this. After all nobody is perfect in everything. We are here to ask question and get the suitable ans.

Hope u dont take my words wrong.

Fair enough, but please have a look at the post I made in a previous thread

http://cr4.globalspec.com/comment/286350/Re-SF6-Circuit-Breaker-Design

It helps explain why I started making these strong comments again in this and other posts (the last time I did on CR4 was about 2 years ago).

In future I will simply ask

"Is this a homework question?"

and

"Why are you asking this question? If you do not know or cannot figure out the answer yourself perhaps you should leave the work to a suitably qualified electrician/engineer/consultant, etc."

and

"Could you please elaborate on WHY you are asking for the answer. Are you new to the electrical field and are interested in learning or are you someone trying to do something you are not qualified to do safely?"

How does that sound. A little less aggressive, but I hope it gets the message across. The message being, the more potentially dangerous the question and answer, the more information needs to be supplied by the poster.

No offense taken by anyone.

there is some kind of protection device to protect transformer such as circuit breaker and fuse. if we use circuit breaker(CB), CB can trip if fault happen. some kind of fault like overcurrent,groundfault, high temperature winding, high temperature oil, high pressure give signal to trip LV switchgear.

for overcurrent, we use CT and 50/51 relay in LV Switchgear,

for groundfault, we use Neutral CT (located in transformer marshalling panel) and 50G/51G relay.

then, if we use fuse, make sure we choose fuse with match curve .

its mean, check melting curve the fuse.

1. Fuse must not be melting when inrush current transformer.

2. Fuse must not be melting when CB (breaker) trip, there is must be coordination between fuse and CB.

Hi Elec-ok

Thanks very much for your response. Grat.full

I thinking may be although you have working in electrical field for a long time. may be you dont work with fuse, CB and etc.

may be this year you have assignment by your boss to another division that care about fuse and CB. may be previous time you only assignmnet to handle about cable, and may be you work in stored, check how many cable used, check time delivery for cable, purchase cable and etc...

or may be in previous time you only handle control lsystem ike PLC, any kind of sensor. so when you commanded to check some "big" protection device. you dont know how to check it. is it right ?

Hi Elect-ok,

Thanks for your understanding.Actually you are partially right. Am an Instrumentation(PLC) guy, but fortunatly got a job into a 90% electrical dept. So am trying to get up to speed with what is going on around me without allowing my greenhorness noticed. Pls if it there is any help(information) you can give to me, it will be highly appreciated.

Best of regards

As you and others here on CR4 can imagine it is very difficult to guess by the limited amount of information that gets included in a new post, what the poster's level of experience is. It really is necessary for people who post questions to include a little more background information on why they are asking the question so the right people get the right answers. In this case all you need to indicate was what you said above, (that you are trying to get up to speed and want a little insight into what you are seeing around you in new line of work).

Since this isn't a homework question (which isn't allowed on CR4 for obvious reasons), you could try goggling "electrical basics" for more information on, well, electrical basics. There are plenty of sites and downloadable electrical basics handbooks available free. The question you originally asked above has been answered here on CR4 a few times also, so you could try looking at previous CR4 posts.

There are plenty of other general electrical questions and answers on CR4, so have a look around.