Diesel Generator

DIESEL GENERATOR

We can discuss about below mentioned topics

-  Daily observation practices

- Peculiar problems & Solutions in DG

- DG Performance improvement  

- Maintenance Challenges

- Filters

- Water content in Diesel identification and removal

-  DG area compliance requirements 

- DG  License  

- DG area

- Safety Best Practices 

Most of the Manufacturers will specify clearly “all safety devices and their function” in DG & "required external Safeties" in their 'O & M Manual'.  Few are

• Temperature Scanner (This will connect with Temperature sensors installed at Alternator Driving end Bearing & different position winding). Above permitted set point it trips the Engine.

• “FAILS to START” relay – it attempts three times, after that disconnects the power to ‘start solenoid’. Respective engineer to check the healthiness of “Battery, Solenoid, Start motor” before resetting this relay.  

• Most of the engines are having built in safety protection “for Engine parameters” 

• For alternator External protections to be maintained at DG panel (or DG Synchronizing panel) based on design type. Few relays are “Multi-function, OC, EF, UV, OV, REF, Reverse power etc.,”

• For operational safety “Air-Muffs must be used by operator when he enters into DG room”.

High water temp. sensor & it will trip @102 or 107 C.

Low lube oil pressure & it will trip @ 180 kpa pr.

Engine Overspeed safety will trip @ 1770 RPM

High Lube oil temp 120 C

High exhaust temp trip @ 475 to 550 C

Since DG system operates in islanded mode, special care on power quality has to be taken. 3rd and 5th Harmonics, DC offset result in often alternator failures.

Best practices on Engine side:

A) Try running the DGs always on optimum load i.e. At least 35% load

B) Run the DGs with the coolant temp of 65'C

C)Never bypass any safety system and exploit the DGs

D) Ensure the Coolant thermostat is operational condition always

E) Watch the color of exhaust smoke for any abnormalities Viz. Dark black, blue and white etc.....

DG is designed @ 0.8 pf

If we switch on more than 10% rated Capitol will lead to failure of   AVR ( Automatic voltage regulator) in DG

If you having more welding load in welding side DG load should not exceed more than 50%

If your site DG loaded motors are DOL started load you will face all type of alternator failure periodically in two to three year once

In my experience in DG set

I had a experience of replacement of all parts of electrical side as follows

Alternator stator/ rotor/ excitation stator/ rotor

AVR

Rotating diode

Surge suppressor etc

Recurring fault in DG??

Mostly high temperature trip.

DG not starting..

Low battery

Suddenly DG shuts off.

Air lock in Fuel Line.

DG RPM Hunting.

Clogging of fuel Line. Fuel filter choking.

What are main four reason of DG hunting??

Mainly because of the fuel Line issues.

In my experience I had this problem twice and both the occasions the root cause traced to fuel Line block.Sometimes it may hunt because of AVR issue also.Faulty Governor can also lead to hunting

Is diodes (IGBT) play any role for the same? DG hunting?

If any issue in igbt firing ckt , sure it will hunting, Because of ckt will not give correct voltage to igbt firing, Then igbt will not working properly, Motor will hunting.