EleMech Pakistan (Pvt) Limited
AUTO SYNCHRONIZING AND AUTO LOAD SHARING OF D. G. SETS.
SEQUENCE OF OPERATION
SINGLE LINE DIAGRAM
When mains are healthy, then both the D.G. Sets remain in the standby mode.
• When mains fail, Line Voltage Monitor (L.V.M.) senses it. Starting pulses are given to the Master D.G. Set. (Master D.G.Set is automatically selected by programme.)
• After satisfactory starting of the D.G.Set 1, voltage is sensed by Generator Voltage Monitor (G.V.M.). If voltage is healthy, then closing signal is given to D.G.1 breaker and it is closed.
• Giving corresponding pulses from the Synchronizing Panel can then automatically start load.
• The load is then sensed by KW transducer in the panel & continuously monitored by Programmable Logic Controller ( P.L.C.)
• Engine & Alternator parameters are also continuously monitored by P.L.C. in the Panel. In case of any fault (e.g. Low Lube Oil Pressure, High Cooling Water Temperature etc.), breaker is tripped & engine is stopped.
• If the load reaches & crosses 80 % of the rated capacity of the D.G. 1, then starting pulses are given to the second D.G.set from P.L.C.
• When D.G.2 starts, then again G.V.M. checks the voltage, and if voltage is healthy, then breaker 2 is closed.
• After closing of the second breaker, Auto load sharing function starts sharing the load between the two D.G.Sets. The percentage of sharing is directly proportional to their individual capacities.
• Since sharing is proportional to their respective capacities, even D.G.sets of different capacities can be synchronized successfully.
• D.G.sets continue to run in Synchronization until the load is above 80 % of any one D.G.set.
• When load comes down below 80 % of any one D.G.set, then the automatic signal is given to that D.G. & then it starts taking the full load.
• After transferring the total load to one D.G. (on which 80 % load is to be connected), the breaker of the second D.G.is opened. Now one D.G.is taking the load, which is less than 80 % of its rated capacity.
• The second D.G. is then stopped after its cooling period.
• The programm is repeated automatically for any variation of the load.
• When mains are resumed, then load is transferred to the mains & both the D.G.sets are stopped after their cooling period.
• The percentage setting is programmable which can be set at any value upto say 90 %
• For stable operation even for sudden variations in the load, programmed timers in PLC are used, which take action only after stabilization of the load.
• The total Automatic operation has a manual override. In manual mode, the total operation can be performed manually.
• Auto load shedding facility can be incorporated by suitable programming of PLC. With this facility, various loads can be brought in or switched off at particular time or for various intervals.
• With the same logic, 3, 4 or 5 sets of equal or different capacities can be Synchronised, with Auto load sharing facility.
ADVANTAGES OF AUTOSYNCHRONISING & AUTOLOAD SHARING
• The total programme is based on load in KW. Hence the actual sharing, starting, stopping & transfers are actual load dependent & not on any other unrealistic parameter like voltage, current. Etc.
• Changing of scheme becomes very easy because of changes are made through software only. There is no changing of wires, adding of components like relays, contactors, which is very time consuming, cumbersome & requiring additional space.
• Along with KW sharing, KVAr sharing & PF sharing is very accurate, because of PLC programming. There is no possibility of any unequal sharing as regards KW, KVAr & PF.
• For any type of load addition or reduction, manual intervention as regards D.G.set operation is not required. However, in case of emergency manual override is possible.
• Special programmers using Real Time Clock (RTC) are possible. With this facility, along with KW dependent programs; day, date & time dependent programmers are possible.
• Because of KW dependent load sharing, optimum utilization of D.G. sets are possible. This increases D.G. sets efficiency & saves lot of fuel.
• D. G.sets are always tried to run with 80 % to 90 % load factor, where we get maximum efficiency of D.G.sets. This is easily possible with our system.
• Because of PLC operation, hardware like relays, contactors, wiring etc is reduced drastically. This reduces fault points & increases the MTBF of the system.
• If any changes are required to be made in future, then there is no need of additional hardware like relays, contactors etc. There is also no need to make new wiring or changes in the wiring. All the changes / modifications can be easily made through software only.
Design &Hosted By: M.Noman Latif