Electricity Troubleshooting

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sts07
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Electricity Troubleshooting

Post by sts07 »

I'm gonna try to explain situation with my limited English knowledge :D . There are two floodlights at foremast and two floodlights at navigation deck on board. Both of floodlight' electricity is supplied through the EMG line. Also we have two more floodlights which are feeded fr main electricity supply but they are unrelated with situation. By the way, we may turn on EMG foremast floodlights and EMG navigation floodlights individually. also we can turn on one of them with main navigation floodlights.However when we try to turn on them at same time, main relay switch of the panel is just cut off. By the way both EMG floodlights have different electricity supply line. Unfortunately there is no ETO on board :D
Big Pete
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Re: Electricity Troubleshooting

Post by Big Pete »

Hi STS07,

I have just noticed that nobody has responded to your post. I am not an Electrician myself, but I will explain how I would approach this problem: -
If the breakers are tripping there are three possibilities: -
A) The incorrect capacity breaker has been fitted.
B) The breakers are operating correctly and the circuit is overloaded.
C) The breakers are faulty and the circuit is operating correctly.


A) Check the Electrical drawings for the original Current rating of the Breaker and compare this with the Breaker that is fitted. Check the Power Rating of the Lights in the original drawings, divide the wattage of the lamps by the Voltage in the circuit to tell you how many Amps the circuit should draw, this should have been less than the rating of the Breaker Fitted. Check the Lamps now fitted in the circuits to see if they are they are the same wattage, and therefore Current, as originally fitted, if the wattage is greater, that could be the cause of the problem
If you have a clamp meter, open the Panel with the breakers in, remove the cover plate and put the clamp meter round ONE of the wires either side of the breakers, watch the current meter when someone switches on the lights and see if the current on the meter is greater than the rated current of the breaker when it trips. If it is the wrong capacity breaker, change it for one of the correct capacity after checking that the Electrical cables and fittings will not overheat under this load.

B) If the Breaker is correct for the Wattage of the Lights and the clamp meter is indicating a greater current is flowing than there should be, then the circuit is being overloaded by a fault. This is most likely an Earth Fault or short circuit, in Deck Light Fittings these problems are often caused by Salt Water getting into Electrical Fittings. Assuming that you have a Multi Meter, with the Breaker in the OFF position, and the switch for each circuit switched on, try measuring the Electrical Resistance between the 2 output wires from the Circuit Breaker to the lights. If the circuit is OK the Resistance of the Circuit should be given by OHM's Law.
Say with a Voltage of 220 Volts a 500 watt Flood light would take a current of 500 Watts /220 Volts = 2.27 Amps
and if a voltage of 220 Volts will drive a current of 2.27 amps through a circuit the resistance should be: 220 Volts / 2.27 Amps = 97 Ohms
If the Resistance is less there is probably a short circuit in the circuit.
If you have a Megga Tester, again with the Breaker off, and the light switched on connect one lead of the Megga to Earth and the other to the two outputs from the Breaker in turn and check the insulation value to Earth, this should be infinite.
If the megga test and or the conductivity results are not what they should be, carry out a close examination of the Flood Lights for signs of Salt, Water and burnt components and clean, repair or replace the flood lights as required.

C) If the breaker is tripping at less than the current it is designed for and everything else is OK replace the breaker with one of the same capacity.

Hope this helps you.

Big Pete.
It is always better to ask a stupid question than to do a stupid thing.
red
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Re: Electricity Troubleshooting

Post by red »

Possible phase reversal ?
Big Pete
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Re: Electricity Troubleshooting

Post by Big Pete »

I recently remembered a problem I had many years ago on a small survey ship which had a similar problem. The Captain had got a shoreside Electrician to wire up some extra lights on deck and the fuses kept blowing, it turned out the electrician thought he was dealing with a live and neutral system, the same as a house, rather than three live phases and had connected the lights across two existing circuits so that when they were switched on they created a short circuit between two different live phases, did you have any additions or alterations made to the circuits by someone who was not trained as a Marine Electrician?
It is always better to ask a stupid question than to do a stupid thing.
popeye62
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Re: Electricity Troubleshooting

Post by popeye62 »

Hello sts07 I'm not an electrician either so just make it safe. Just to be clear, the emergency floodlights in normal conditions are supplied by the main generators via the emergency switchboard (EMSB). The main switchboard (MSWB) is tied to the EMSB with a breaker that drops out when 0 voltage is detected (blackout). The source of the power is not important but both the MSWB and EMSB have insulation monitoring. Are there any earth faults showing on the EMSB? The two lights have different 'supply line' probably because they are coming from two different emergency lighting panels. The EMSB is probably split by a transformer into a 440VAC and a 220VAC and possibly a 24VDC sections. If there is a problem it is likely on the 220VAC. All of the previous ideas apply but I would be careful using Ohms Law on an AC circuit which, depending on the type of lamp, will have some inductance adding to the resistance (R) to create impedance (Z). High discharge lamps can draw high currents if their ballasts or power factor correction have failed. Earth faults don't usually shut down systems on ships but two earth faults on two different supply lines will. Sorry, sts07 but my advice is have an electrician waiting at the next port, if you are on a tanker insist on an electrician at the next port. Next time you put the EMG on load, try those lamps and plan for a service of the switchboards including thermographic for poor connections.
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