Visit of Saritow Spinning Mills Ltd's Power Plant

Visit of Saritow Textile Mills Ltd Power Plant 

Pakistan is facing worst blackouts of the history due to a large difference of production and consumption of power. They are becoming more and more worse with time. These blackouts are specially affecting industries so a lot of industries are installing their own small scale gas or oil fired power plants to meet their energy needs. Although this adds extra cost to purchase and maintain their own plants but still severe black outs encourages and even small industrialists are making their own power plants.

Saritow Spinning Mills Ltd Lahore also has their own 10 MW power plant. Last day I visited this power plant and observe synchronization of plant with WAPDA supply. Here I going to write whatever I have seen.

This power plant has 3 gas fired power plants and one heavy furnace oil (HFO) plant.  Three gas power plants have power capacity of 5.10 MW and HFO have power capacity of 5.08 MW. So there are two sections, one for three gas generators with their fuel supply lines and exhaust. Gas exhaust is 500C average temp and this exhaust is used to run a boiler which warms HFO fuel in winter. Three gas generators are very compact and occupy much less space than HFO.  Also there per unit price is less than HFO but as gas is only available for 8 hours a day so they have HFO as a backup.  Second section is HFO, which has furnace oil storage place then a cleaning and settling tower and also have cooling towers. To keep its fuel warm, they have a boiler which uses exhaust of three gas engines. 
Overview of Generators:

Gas Engine Section:

This section is recently added so it has quite modern automatic control and synchronization system.  3 gas fired generators have a total capacity of 5.08 MW. Their Exhaust is being used by a boiler as mention earlier.

3 gas generators and their exhaust system

Exhaust system, on the left side 3 gas generators and on the right side HFO exhaust

HFO section:

This section occupies major space of the power station also its quite noisy. Its max power capacity is 5.10 MW.

It has a storage space where all the oil is stored. 

HFO storage tank

This fuel is then brought to two towers where it settled and cleaned to use it in HFO generator. Generator  looks something like this.

Settling and cleaning tank for HFO

HFO generator

Then there are some cooling towers.

Cooling tower for HFO generator

So this is mechanical overview of the whole thing. Now coming to the Electrical side.

Some technical data for this HFO and gas engine is is in this document…

Some Data about Power plant:

This taken was taken from power plant and they are owner of it. Here it is presented to give a practical view of genration.

1. Power production report 
2. Gas per unit price 
3. HFO daily report 
4. Loadsheding schedule 
5. Technical details of installed generators 

Overview of Electrical side of the system:

Electrical Side of Power station:

Electricity produced is used by two section of spinning mill with a total demand of 4.5 MW almost. Both gas and HFO generators  have a control panel , a synchronization panel and some circuit breakers , bus bar , power transformer and some other electrical equipment. Preference order for power is as follow

1.     Gas Fired generators

If gas is available, they prefers to produce their own electricity as per unit cost is less than utility   electricity but gas is available only for 8 hours a day.

2.     Utility Electricity

Second preference is WAPDA supply.

3.     HFO generator

In case, if both supplies go out, this is uses as a backup. Mostly WAPDA and gas companies give schedule for load shedding, so it started when both goes out. 

Mostly generator is used with utility supply so it need synchronization, which will be mention in later part of the discussion.

Their are three important parts of the system that makes system to remain connected with both WAPDA and their own generators. first one is Control panel which has readings of the system and also alarms for faults, second is synchronization panel which helps to synchronize both supplies and third are some electrical equipment that are used to do this operation like circuit breakers,  power transformers etc. Here are some details.

Control Panel

Both generators have a control panel that have most of the readings, fault indication etc. HFO is installed in older style so its panel is analog with a lot of buttons and led lights to operate it manually and LEDs indicating faults or which is part is working well or not.

Control panel of HFO generator

But three gas generators are recently installed so they have automatic and digital control panel with LCD indicating values with quite comprehensive way.

Control panel of gas generator

LCD in the middle of panel comprehensively showing all the current values of the system. They shows all the things in this way. A windows XP system is installed in this which monitors all the values coming and shows it on the screen.

Then you can select any window to see more detailed view like this..

There are a lot of values like temperature of exhaust, temp of fuel, fuel supply etc.

Synchronization panel:

System uses both utility supply as well as their own production so both need to be synchronized. Here is a picture of bus bar with all gens and grid supply.

Single line diagram of generates and Utility grid supplying energy to the mills

3 gas generators, 2 power transformers, 1 HFO generator  and 2 WAPDA feeders of 11kv are connected to bus bar by a Vacuum circuit breaker.

So as power is being fed by 3 different sources so it need synchronization.

In an alternating current electric power system, synchronization is the process of matching the speed and frequency of a generator or other source to a running network. An AC generator cannot deliver power to an electrical grid unless it is running at the same frequency as the network. If two segments of a grid are disconnected, they cannot exchange AC power again until they are brought back into exact synchronization. [Wikipedia]

In order to synchronize a generator to the grid, four conditions must be met:

1. Phase Sequence
2. Voltage Magnitude
3. Frequency
4. Phase Angle

Read more about synchronization here...

Same process is used in this power station. 3 gas generators have automatic synchronization panel which take care of all these parameters. Only thing need to do is to on genrator supply and press a button to convert load from Wapda to generator. 

And display 

  
But other generator also called HFO generator have a manually driven synchronization panel like this. So in this panel all things like voltages , rpm etc are  done by hand.

Synchronization panel of HFO generator

Electrical Equipment:

Although there were a lot of equipments like power transformers, circuit breakers motors, cooling tower things but I only visited VCB (vacuum circuit breaker). They are just used to connect or disconnect bus bar with generator or 11kv line.

A vacuum circuit breaker is such kind of circuit breaker where the arc quenching takes place in vacuum. The technology is suitable for mainly medium voltage application. For higher voltage vacuum technology has been developed but not commercially viable. The operation of opening and closing of current carrying contacts and associated arc interruption take place in a vacuum chamber in the breaker which is called vacuum interrupter. The vacuum interrupter consists of a steel arc chamber in the centre symmetrically arranged ceramic insulators. The vacuum pressure inside a vacuum interrupter is normally maintained at 10 ^{- 6} bar. [read more here]

VCB connected to generator 2 on incoming side

By the way here are some of my pictures infront of genraotr of power plant ;)