Electrical Power Distribution and Control

Electrical power is controlled and distributed by assemblies. Each assembly-main distribution assembly, power controller assembly, load controller assembly and motor controller assembly-is an electrical equipment container or box.

Circuit breakers

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.

 Low voltage circuit breakers for control supply

Low voltage (less than 1000 VAC) types are common in domestic, commercial and industrial application, include:

• MCB (Miniature Circuit Breaker)—rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category.

• MCCB (Molded Case Circuit Breaker)—rated current up to 2500 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.

• Low voltage power circuit breakers can be mounted in multi-tiers in LV switchboards or switchgear cabinets.

Medium-voltage circuit breakers for Generator output

 Front panel of a 1250 A air circuit breaker
manufactured by ABB. This low voltage power circuit
breaker can be withdrawn from its housing for
servicing. Trip characteristics are configurable via DIP
switches on the front panel.

Medium-voltage circuit breakers rated between 1 and 72 kV may be assembled into metal-enclosed switchgear line ups for indoor use, or may be individual components installed outdoors in a substation. Air-break circuit breakers replaced oil-filled units for indoor applications, but are now themselves being replaced by vacuum circuit breakers (up to about 35 kV). Like the high voltage circuit breakers described below, these are also operated by current sensing protective relays operated through current transformers. The characteristics of MV breakers are given by international standards such as IEC 62271. Medium-voltage circuit breakers nearly always use separate current sensors and protection relays, instead of relying on built-in thermal or magnetic overcurrent sensors.

Medium-voltage circuit breakers can be classified by the medium used to extinguish the arc:

• Vacuum circuit breaker—with rated current up to 3000 A, these breakers interrupts the current by creating and extinguishing the arc in a vacuum container. These are generally applied for voltages up to about 35,000 V, which corresponds roughly to the medium-voltage range of power systems. Vacuum circuit breakers tend to have longer life expectancies between overhaul than do air circuit breakers.

• Air circuit breaker—rated current up to 10,000 A. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. Usually electronically controlled, though some models are microprocessor controlled via an integral electronic trip unit. Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.

• SF6 circuit breakers extinguish the arc in a chamber filled with sulfur hexafluoride gas. Medium-voltage circuit breakers may be connected into the circuit by bolted connections to bus bars or wires, especially in outdoor switchyards. Medium-voltage circuit breakers in switchgear line-ups are often built with draw-out construction, allowing the breaker to be removed without disturbing the power circuit connections, using a motor-operated or hand-cranked mechanism to separate the breaker from its enclosure.

Control Relays

                                                     AC coil control relay

Relays are used in control panels to control a circuit by a low-power signal, or where several circuits must be controlled by one signal. A type of relay that can handle the high power required to directly drive an electric motor is called a contactor.

Latching relay & Reed relays

 

Types of control relays used in a power plant.

1.     Latching Relay

2.     Reed Relay

3.     Contactor Relay

4.     Solid-State Relay

5.     Solid State Contactor Relay

6.     Mercury-watted relay

7.     Polarized relay

                                                               Solid state relay

 Protection Relays

Protection relays used to protect equipments (Alternator, Transformer, and Engine) and power supply related issues.

Types of protection relays.

1.     Over current relay

2.     Earth fault relay

3.     Reverse power relay

4.     Under voltage and over voltage relay

5.     Multifunctional relay

6.     Differential relay

7.     Over frequency and under frequency  relay

8.     Buchholz relay

 

ALARMS AND WARNINGS

Shut-down functions with display:

• Low lube oil pressure

• Low lube oil level

• High lube oil level

• High lube oil temperature

• Low jacket water pressure

• High jacket water pressure

• High jacket water temperature

• Over speed

• Emergency stop/safety loop

• Gas train failure

• Start failure

• Stop failure

• Engine start blocked

• Engine operation blocked

• Misfiring

• High mixture temperature

• Measuring signal failure

• Overload/output signal failure

• Generator overload/short circuit

• Generator over/Undervoltage

• Generator over/Underfrequency

• Generator asymmetric voltage

• Generator unbalanced load

• Generator reverse power

• High generator winding temperature

• Synchronizing failure

• Knocking failure

Specifications

 A- Open Cooling System For J/W & A/C Circuits’ Specifications

 Cooling Tower For J/W +A/C Combined Circuit

. Cooling capacity                            877500/HR        

. Flow rate                                       2925 LPM.

. Fan motor HP                               7.5 hp (approx)            

. Range                                             08°C

. Approach                                       3°C

. Wet bulb temp.                             30°C

. Water Outlet Temperature           33 °C (From the Cooling Tower)

. Water Inlet Temperature              41°C (To the Cooling Tower)

. Qty                                                  1 No. / Genset (Total 5 Nos.)

 Pumps For J/W+A/C Combined Circuit

. Type:                                               Centrifugal 100 m3 / hr.

. Flow rate:                                      2.5 bar (approx.) it may vary w.r.t. piping route 15 kW

. Head:                                             (may be revised w.r.t. supplier)

. Motor Power:                                15 kW

. Qty:                                                          7 Nos. (Two for standby)

 Ventilation Fan Specifications

nduced Draught Fan

• Flow:                                             30,000 CFM (cubic ft / minute)

• Static Pressure                                       01 inch of Water

• Motor Hp:                                    5.5

• Fan Rpm:                                     960

• Qty:                                               02 Nos. / Genset

 Exhaust Fan

• Flow:                                             20,000 CFM

• Static Pressure                                       01 inch of Water

• Motor Hp:                                    5.5

• Fan Rpm:                                     960

• Qty:                                               1 No. / Genset

 Lube Oil Tank

Lube Oil Tank have a volume of 220 Liters

 Lube Oil Pumps Specification

-Pumps For Lube Oil

• Type:                                             Gear type

• Flow rate:                                     20-30 lit. /min.

• Motor Power:                              01 eKW

• Qty:                                               1 Nos./ Power House

 Motor Control Center Specification

1- Feeder For Combined (Ht & Lt) Coolong Tower Circuit Pump

Motor Power: 15 HP (approx.)

It consist of Star Delta Starting System, having

1 - Motor Breaker

2 - Fault Contact

3 - Mains Contactor

4 - Timer

5 - Relays

6 - M-O-A. Selector Switch

7 - Auxiliary Contact for Breaker

8 - Control Fuse

9 - Indications (On-off-trip)

2- Feeder For Cooling Tower Fan Motor

Motor Power: 7.5 HP (approx)

It consist of DOL Starting Circuit having

1 - Motor Breaker

2 - Fault Contact

3 - Mains Contactor

4 - M-O-A Selector Switch

5 - Control Fuse

6 - Auxiliary Contact for Breaker

7- Indications (On – Off-Trip)

3-  Feeder For Induced Draught Fan Motor

Motor Power: 2 x (Power ratting of each motor corresponding to 15000 CFM to be checked from the supplier)

It consist of 2 x DOL Starting Circuits, each having

1 - Motor Breaker

2 - Fault Contact

3 - Mains Contactor

4 - M-O-A Selector Switch

5 - Control Fuse

6 - Auxiliary Contact for Breaker

7- Indications (On – Off-Trip)

4- Feeder for Exhaust Fan Motor

Motor Power:     7.5 Kw

It consist of DOL Starting Circuit having

1 - Motor Breaker

2 - Fault Contact

3 - Mains Contactor

4 - M-O-A Selector Switch

5 - Control Fuse

6 - Auxiliary Contact for Breaker

7- Indications (On – Off-Trip)

5- Feeder For Lube Oil Pumps’ Motor

Motor Power: 2 X 1 eKW (approx.) It

Consist of 2 x DOL Starting circuit, each having

1 - Motor Breaker

2 - Fault Contact

3 - Mains Contactor

4 - M-O-A Selector Switch

5 - Control Fuse

6 - Auxiliary Contact for Breaker

7- Indications (On – Off-Trip)

6- Circuit Breaker For Genset Control Panels

5 X 50 Amps (3 X 400 / 213V) MCB circuit breaker / engine with thermal protection.

10 x 20 Amps (231 V) MCB Circuit Breaker for Air-Conditioning & Lighting

7- Incoming circuit breaker with change over system for

mcc panel

3 X 400V, MCB with thermal protection. Its capacity is as per above various circuit breaker’s Amps.

 Optional Contacts:

1- Load Shedding Contact: (Optional)

Normally Open Contact of a breaker which customer wants to cut off for Load Shedding Purpose

2- Collective Trouble Contact: (Optional)

Normally Open Contact of a breaker which customer wants to be cut off at the time of unexpected failure of any unit. (Thus over load shut down may be prevented at that situation)

 Power Cables

• 5 x 300 mm2 / phase + 3 x 300 mm2 for neutral conductor from alternator to the bus bar. (Size of power cable may vary with respect to the site conditions)

  Warning/ Shut Down Indicators (Optional)

Horn 24 V dc

Rotation Lamp 24 V dc

The above specification for MCC is for reference purpose and this is the minimum Specification for any MCC panel.

The various motors rating may vary from suppliers to suppliers

Design MCC panel after having rating of each motors from supplier.

For all motors with capacity greater than or equal to 10 HP Star-Delta starting will be used for all motors with capacity less than 10 HP DOL starting will be used.

Customer Scope of Supply

 Self-excited self-regulated three phase generator

The generator consists of the main generator (built as rotating field machine), the exciter machine (built as rotating armature machine) and the voltage regulator with cos. phi-regulator, which is powered by a permanent magnet pilot exciter.

 Main components

• Main stator with frame

• Main stator with 2/3 pitch winding to eliminate neutral currents of 3rd order

• Terminal box includes main terminals plus auxiliary terminals for thermistors connection and control of Regulator

• Main rotor with sufficiently sized shaft dynamically balanced as per VDI 2060, Grade Q1

• Drive end bracket with bearing

• Non-drive end bracket with bearing

• Exciter unit with permanent pilot exciter

• Power factor controller

• Voltage regulator

 Electrical data and features

• Voltage adjustment: +/- 5% rated voltage (+/- 10% short-time for synchronizing)

• Static voltage accuracy: +/- 1% at no load to full load and power factor 0.8-1

• Speed variation +/- 3%, cold and hot machine

• Maximum deviation of wave form according to VDE is 5% phase to phase at open circuit

• Generator suitable for parallel operating with mains and other generators

• Sustained short circuit current at 3-pole terminal short circuit: minimum 3 times rated current for 5 Seconds.

• Overload capacity according. To IEC 34 - I/VDE 0530

• According to VDE 0530 the overspeed test ensues with 1.2 times of rated speed for 2 minutes.

Additional components:

• Electronic voltage regulator

• Electronic power factor regulator

• 3 thermistors for winding temperature monitoring

The following alternator supervisions are integrated with the multi-transducer (max. 8 functions Simultaneous):

• Overload/short-circuit [51], [50]

• Over voltage [27]

• Under voltage [59]

• Asymmetric voltage [64], [59N]

• Unbalance current [46]

• Failure Excitation [40]

• Over frequency [81>]

• Under frequency [81<]

• Lockable operation mode selector switches positions:

• "OFF"

No operation is possible, running set will shut down;

Auxiliaries and Startup

When the module is not in operation (generator cb is open) the auxiliaries have to be supplied by a safe

Power supply to ensure

- Preheating

- loading of batteries

After the generator cb of the module is closed, the supply of the auxiliaries may be switched to the bus bar.

 Equipments

 Starting Equipment:

Starter batteries: lead/acid

24 V, 200 Ah per module.

Battery Charger:

24 V, 40 A:

With integrated control system power supply 24 V =, 18 Ah. Used for module controller.

Control System Power Supply:

24 V=, min. 22 - max. 30 V (inclusive of ripple) at terminal. Max ripple Uss = 2,4 V.

 Control voltage for module control cabinet from starter batteries

(Diode encoupled).

Control voltage for common cubicles (interlock panel ...)

Provided by starting batteries, connected via diodes.

 Jacket Water Preheating:

3x 400 V, 50 Hz, 6 kW

Thermostatically controlled between 55 – 60°C.

Jacket water preheating ON when Engine in OFF position.

Jacket Water Circulating Pump:

231 V, 50 Hz, 245 W:

Pump operates during engine shutdown and auxiliary cool down phase.

Technical specification of the control

 Intercooling Water Pump:

3x 400 V, 50 Hz, 1550 W:

Pump operates during module operation and during 5 minutes cool down run.

 Pre-Lube and Cool Down Oil Pump:

1x 24 VDC, 180 W:

Controlled by module PLC.

Operating time > 1 minute before engine start. Once engine speed exceeds 800 rpm, the pumps is switched off.

After module stop, the pump continues to operate for 40 minutes in order to cool down the turbocharger.

Additionally, the pumps can be manually controlled in order to preheat the lube oil.

Solenoid valve SOV 13: 1x 24 VDC, 22 W

At engine start with a jacket water temperature < 86°C the valve is open

At engine operation and jacket water temperature > 86°C the valve is closed. If the temperature decreases below 84°C the valve is open

During the 20 minutes auxiliary cool down run the valve is open.

 Start up procedure for Generator Sets

1. Check all electrical connections in generator and panel.

2. Check fuel system and bleed out any air. Make sure supply and return lines are open.

3. Check exhaust system for proper installation

a. Dry exhaust

b. Wet exhaust

4. Check engine ventilation system.

a. Industrial application

b. Marine application

5. Check for proper fluid levels.

a. Heat exchanged units, seawater is at pump.

b. Keel cooled units.

Most keel cooled units will overheat on start up, because of air in the system. This will be indicated by a rise above 200 degrees on the engine temperature. Water pump inlet will be hot and the expansion tank discharge will be cold.

Method to correct this:

a. On a cold engine, fill coolant system slowly. Using vent on side of thermostat housing, vent air out until water flows through vent. Also bleed air from vent on turbo, on turbocharged units.

b. On a hot engine, with engine running, carefully keep adding coolant with the thermostat vent open until engine temperature drops to normal and unit stops taking coolant. Close vent. Be careful of engine burping coolant and air out the filler opening. Also double check turbo vent for air.

c. Radiator units, coolant should be approximately 1 inch below top of radiator.

6. On some installations, keel coolers are installed in such a manner that the cooler slopes upwards away from the inlet and outlet. In this case it is the responsibility of the boatbuilder to install a bleed screw at the high point of the cooler.

7. Start unit at no load.

8. Check AC output voltage at the generator, for proper output. And make sure the generator output is the proper voltage and phase that is needed by the boat or building.

9. Check AC voltage regulator field voltage. a. 10 to 18 volts DC approximately – with no load.

10. If voltage regulator fuse or breaker blows, check wiring and make sure generator is not connected to the load source.

11. If 8, 9, and 10 are okay then check panel meters for proper operation.

12. Then apply load and note operation of equipment for normal events.

13. Fill out paperwork.

Paralleling Procedure

 Preliminary steps

Step 1. Start unit no. 1 and record no load AC voltage, hertz, and DC field voltage. Close line circuit breaker to the buss and load. Then record again the load AC voltage, hertz, and voltage regulator DC field voltage in steps of 25% load if possible.

Step 2. Start unit no. 2 and record no load AC voltage, hertz, and DC field voltage then check phase rotation to match the buss. Remove unit no. 1 from the buss and put unit no. 2 on the buss, recording loaded AC voltage, hertz, and voltage regulator DC field voltage. In the same load steps as on first unit.

The purpose of doing the above is to match AC voltage between the units. So when you are done with the settings both units should have the same no load voltage and they should droop the same amount of voltage under the same load conditions. And the same goes for the speed droop. The AC voltage stability on all units should be about the same to minimize cross current at no or light load conditions.

A word on cross current, the voltage regulator should have the paralleling option to provide regulator droop under load conditions, if one units voltage goes up and the other units voltage goes down, reverse the “ct” leads at the regulator to match.

 Paralleling procedure manual, lights or scope

Generator paralleling

After preliminary adjustments are made you should not have to do them again, unless for some reason the values change. Always record readings and keep, in maintenance log.

Synchronization steps

Step 1. With one unit on the buss and carrying the load, start the second unit.

Step 2. Turn on the sync. Lights or scope.

Step 3. Observing lights adjust speed of second unit to be slightly faster than the unit on the buss. The lights will go on and off slowly (bright to dark).

Step 3a. With the sync. scope adjust the off line unit’s speed so that the scope rotates clockwise slowly.

Step 4. At the instant the lights go darkest, close the second unit’s circuit breaker to the buss.

Step 4a. With the sync. scope, as it rotates between the 11:00 and 1:00 position instantly close the second units circuit breaker to the buss.

Step 5. At this point you can balance loads by adjusting engine speed. Load imbalance is a function of engine speeds up or down.

NEVER ADJUST VOLTAGE AFTER UNITS ARE IN PARALLEL!!!!!!!!!!