FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A system and method to detect inter turn short circuit fault in generators
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Pasumarthi Umamahesh and Mylavarapu Ramamoorty of Crompton Greaves Ltd, Electronics Design Centre, C G Global R&D Centre, Kanjur Marg, Mumbai, Maharashtra, India; both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed

Field of the Invention:
This invention relates to the field of electric generators and health detection systems for electric generators.
Particularly, this invention relates to a system and method to detect inter turn short circuit fault in generators
Background of the Invention:
An electric generator or electric motor consists of a rotor spinning in a magnetic field. The magnetic field may be produced by permanent magnets or by field coils. In the case of a machine with field coils, a current must flow in the coils in order to generate the magnetic field; otherwise no power is transferred to or from the rotor.
Major failures in generators are related to stator winding faults, among which inter-turn short circuit faults are common in nature. Insulation breakdown between the individual winding coils may result in the shorting of one or more turns of stator windings. These inter-turn short circuit faults may produce excessive heat that may eventually lead to severe phase to phase fault or even phase to ground fault.
According to the prior art, there is no system or method to detect the inter turn short circuit fault in generators.
Therefore, there is a need for a method and a system to detect inter turn short circuit fault in generators.

Objects of the Invention:
An object of the invention to provide a method and system to detect inter turn short circuit fault in generators.
Another object of the invention is to provide a method and system to detect inter turn short circuit fault in generators, particularly to detect internal negative sequence voltage in order to identify inter turn short circuit fault in generators.
Yet another object of the invention is to provide a faster and accurate detection technique to detect inter turn short circuit fault in generators.
Summary of the Invention:
According to this invention, there is provided a system to detect inter turn short circuit fault in generators, said system comprises:
a) internal network sequence voltage determination means adapted to determine voltage of the internal sequential network;
b) external network sequence voltage determination means adapted to determine voltage of the external sequential network;
c) comparator means adapted to compare said internal network sequence voltage with a reference range which tends to zero value; and
d) determination means adapted to determine inter turn short circuit fault if said output of said comparator means is positive.
According to this invention, there is also provided a method to detect inter turn short circuit fault in generators, said system comprises the steps of: i. determining voltage of the internal sequential network; ii. determining voltage of the external sequential network;

iii. comparing said internal network sequence voltage with a reference range which
tends to zero value; and iv. determining inter turn short circuit fault if said output of said comparator means
is positive.
Brief Description of the Accompanying Drawings:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic block diagram of the fault sensing technique i.e. the system to detect inter turn short circuit fault in generators; and
Figure 2 illustrates a detailed schematic block diagram for the system.
Detailed Description of the Accompanying Drawings:
According to this invention, there is provided a system and method to detect inter turn short circuit fault in generators.
Figure 1 illustrates a schematic block diagram of the fault sensing technique i.e. the system to detect inter turn short circuit fault in generators;
In accordance with an embodiment of this invention, there is provided an internal network sequence voltage determination means (INSVM) adapted to determine voltage of the internal sequential network.
In accordance with another embodiment of this invention, there is provided an external network sequence voltage determination means (ENSVM) adapted to determine voltage of the external sequential network.

In normal condition the internal network sequence voltage seen from mains is zero. . In case of any external fault or unbalance at mains, the external network sequence voltage at mains is present. But, in external fault and in unbalanced conditions, internal network sequential voltage is in series with external network sequence voltage. So, resultant internal negative sequence voltage will be zero.
Whereas, in cases of an inter turn short circuit, even though external network sequential voltage is in series with internal network sequential voltage, even due to slight unbalance created by the short circuit, it can be detected from internal network sequence voltage, which is negligible (tending to zero value, but not zero) while seeing from external negative sequence voltage.
In accordance with another embodiment of this invention, there is provided a comparator means (CM) adapted to compare internal network sequence voltage with a reference range (Ref) which tends to zero value, but not zero value. If this detection in this range is positive, inter turn short circuit condition in the generator can be detected.
Figure 2 illustrates a detailed schematic block diagram for the system. From a generator (G), output is given to two parallel output streams and sequence of blocks; firstly through a voltage computation means (VCM) and secondly through a current computation means (CCM). Current and Voltage of each phase may be sensed in their vector format, for three phase power supply. Values from voltage computation means (VCM) are independently provided to negative sequence voltage computation means (NSVCM) and values from current computation means (CCM) are independently provided to negative sequence current computation means (NSCCM). Outputs from the negative sequence voltage

computation means (NSVCM) and the negative sequence current computation means (NSCCM) are collated in an external negative sequence computation means (ENSM). The ENSM block also receives general internal inductance (I) of the generator (G). The value from the ENSM block is compared with a reference energy value (Ref) by means of a comparator (CM) in order to receive an output (O/P) which helps in detecting inter turn short circuit condition in the generator.
Table 1 represents results using the system, in a variety of scenarios.
Table 1

Internal fault Detected Parameter
Case Ext fault Kl K2 K3 En Magnitude
Normal 1 1 1 1 0
Normal 1 0.5 0.5 0.5 0
Inter turn fault 1 0.3 1 1 0.1347
External fault 0.99 1 1 1 0.02503
External fault 0.95 1 1 1 0.004388
External fault 0.99 0.5 0.5 0.5 0.02194
External fault 0.95 0.5 0.5 0.5 0.02617
External fault 0.95 1 1 1 0.008142
External fault 0.99 0.5 0.5 0.5 0.02295
External fault 0.95 0.5 0.5 0.5 0.05005
External fault 0.9 1 1 1 0.04388

It can be seen that, when there is no internal fault, for any external fault or load unbalance,the magnitude of En is very close to zero. The system of this invention detects such conditions and faults.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A system to detect inter turn short circuit fault in generators, said system comprising:
a) internal network sequence voltage determination means adapted to determine voltage of the internal sequential network;
b) external network sequence voltage determination means adapted to determine voltage of the external sequential network;
c) comparator means adapted to compare said internal network sequence voltage with a reference range which tends to zero value; and
d) determination means adapted to determine inter turn short circuit fault if said output of said comparator means is positive.
2. A method to detect inter turn short circuit fault in generators, said system comprising the steps of:
i. determining voltage of the internal sequential network; ii. determining voltage of the external sequential network; iii. comparing said internal network sequence voltage with a reference range
which tends to zero value; and iv. determining inter turn short circuit fault if said output of said comparator means is positive.