Products

GEN MASTER – For DG set/Utility application with dual control

Use of ‘datar’ Gen Master with DG Set and Utility Power –

It is the load which lowers the power factor of the power delivering system. When power is drawn from utility, it is desirable to improve the power factor to unity. But when the power drawn from the DG Set, the power factor is not allowed to be improved beyond 0.95 as recommended by the DG set manufacturer. Also after the DG set is started, the load is increased on it gradually. While the load is less and if a fast switching APFC system is connected to it for PF correction, due to capacitor connection the DG set runs overexcited and starts hunting. These specific requirements does not allow the customer to use the same APFC system with DG set that is in use while power is drawn from utility. The customer needs to have two different APFC systems i.e. one for using on utility and other one for DG set, calling for additional investment.

‘datar’ Gen Master comes with the APFC relay with duel setting. The customer can preset the target power factor that is to be achieved while using DG set or utility power. Customer need to preset it only once and leave it to the controller to achieve the target PF. The controller target power factor setting automatically changes over to another setting whenever power fails and load is transferred from utility to DG Set. The APFC relay that comes with Gen Master has the program not allowing to switch on the capacitor banks until the load on DG set loaded upto 15-20%.

Load Current Sensing –

The Load CTs are placed at the common point of supply, going to the load. If this is not possible then two sets of CTs are required, one to be placed at utility side incomer and another set at DG set side incomer. When utility power fails, the contactor will automatically change over to DG set side CTs. The signal is taken from DG AMF panel and will have interlocking with APFC system.

Benefits –

These particular features incorporated in the ‘datar’ Gen Master, enables the customer to derive following benefits.

Compatibility of ‘datar’ Gen Master with DG Set –

‘datar’ Gen Master is the only APFC System, which can be put into the electrical network while power is being fed from the DG Set. This has been achieved through constant and persistent efforts of our R & D to develop a system having following features –

In conventional Automatic Power Factor Correction System when capacitor is switched ON with the help of contactor, surge of inrush current drawn from the generator is as high as 200 times the rated current. This result in voltage dip and increases the excitation to stabilize the level of voltage generated. This in turn causes over-voltage in the network and the generator works in unstable mode, which further causes hunting. ‘datar’ has developed RTPFC System which switches ON the capacitor on zero point on AC waveform so that the inrush current is totally eliminated and above phenomenon does not occur.

In the conventional Automatic Power Factor Correction System usually power factor of only one phase is sensed and the decision of capacitor insertion/ withdrawal is based on this measurement which may cause over compensation or under compensation of the network. Over compensation is not desirable as exciter circuit faces problem due to over compensation. In case of under compensation the generator capacity is not utilized fully. In conventional system there is an intentional unavoidable delay of two minutes provided between the sensing and the corresponding correction which may cause under/ over compensation continuously.

‘datar’ Gen Master continuously monitors the P.F., Current, kVAr Compensation required for each phase individually and based on the data collected it corrects the power factor on cycle to cycle basis by switching ON the maximum capacitor instantaneously by pre-programmed permutations and combinations of the capacitor banks steps in order to achieve the set target P.F. While doing so it takes utmost care of not to overshoot P.F. beyond the set value and thus there is no over compensation / under compensation. Due to the above features of ‘datar’ Gen Master the DG Set can be additionally loaded and there is no over compensation or under compensation and there is no chance of over excitation occurring due to introduction of unnecessary capacitors. However, customer is still in a position to enjoy the benefits of improved P.F., which helps in drastic load growth and reduction in fuel consumption proportionately.

DG Set Loss Reduction by ‘datar’ Gen Master –

Reducing the current output from alternator without altering the loading conditions can reduce the alternator losses. Improving the power factor at the output of the alternator can conveniently do this. Hence, improvement in the power factor in alternator leads to reduction of fuel consumption in DG sets. Conventionally capacitors are not used along with DG sets, because by using fixed capacitors there is a danger that the PF can become leading under lightly loaded condition which is highly undesirable in DG set operation. And also when capacitors are connected to the network, heavy current, as high as 200 times rated current, may be drawn through the DG set which has got harmonics contents also. This leads to polluting the network and which is undesirable. Hence only Automatic Power Factor Correction System of datar Gen Master should be used with DG sets. The target Power Factor can be set to 0.93 to 0.95 for optimum performance.

The following example gives an approximate calculation which shows the impact of power factor improvement on reduction in alternator losses and accrued savings in Diesel consumption.

Consider a 3 Phase, 415 V, 50Hz, 320 kVA DG set used in an industry for 3000 hours/year with an average load of approximately 250 kw at 0.86 PF. What is the fuel/cost saving if PF is improved to 0.95? The full load copper loss of the alternator is 5 kW and average yield of the DG set is Rs. 3 kWh/liter of fuel.