Frankfurt (Germany), 6-9 June 2011  New challenges in relay testing More complex impedance relay characteristic More complex differential relay characteristic No more than 8 words per line Increased number of functions to test New IEDs require a more accurate simulation of the electrical phenomena Author Name – Country – Session ….. – Paper ID Advanced Distance Relay Modeling and Testing

Frankfurt (Germany), 6-9 June 2011 Distance relay modeling  Unlike old relays, new impedance characteristics are more complex  The test engineer must deeply know all relay features  The new Toshiba GRZ100 has a very challenging impedance characteristic

Frankfurt (Germany), 6-9 June 2011  The relay characteristic is not just a series of lines and arcs  It is the intersection of different comparators A characteristic like thisIs the result of an intersection

Frankfurt (Germany), 6-9 June 2011  In RIO format, that shape is defined as LINE , , 75 ARC , , 10, , LINE , 18, 180 ARC , , 10, , 165 LINE , , -60 LINE 0, 0, -10 ARC , , 10, 265, It is evident it is not something that can be easily done by hand.

Frankfurt (Germany), 6-9 June 2011 The importance of a library...  For this reason, several relay test set manufacturers offer a library  The purpose is to automatically define that sequence of arcs and lines which depends on the extension of the circular characteristic And until now, nothing new

Frankfurt (Germany), 6-9 June 2011 New ways to define the characteristics  The characteristic is always defined as a result of the intersection of different comparator.  The result is a series of line and arcs  And it represents just one single characteristic... But what if we use two characteristics to represent one ?

Frankfurt (Germany), 6-9 June 2011 Use the same (almost) method of the relays...  As we already said...  So that we can say, if that is zone 1 Zone 1 = Z1 MHO ∩ Z1 QUAD A characteristic like thisIs the result of an intersection of 2 characteristics This MHO And this poligonal

Frankfurt (Germany), 6-9 June 2011  So that if the draw two simple char 1. Zone 11: MHO 2. Zone 12: Poligonal  The nominal char can simply been calculated as Znom = Min (Zquad, Zmho)  The testing software must simply evaluate 2 impedance values and take the minimum

Frankfurt (Germany), 6-9 June 2011 In the same way... A Characteristic like the SEL321 will be union of 2 shapes + =  In this case: Zone 1 = Z1 MHO U Z1 QUAD  and... Znom = Max (Zquad, Zmho)

Frankfurt (Germany), 6-9 June 2011 This is very useful in many cases ... Like in the general fault criteria and the General fault criteriaLoad encroachment

Frankfurt (Germany), 6-9 June 2011 Conclusion for part 1  This approach will enhance the productiveness of the technicians  But it will change the method of exporting the impedance relay nominal characteristic  formats like the actual RIO would be insufficient In fact, although it makes possible to define whatever number of zones, it is not giving information whether a single zone is the combination of more shapes.

Frankfurt (Germany), 6-9 June 2011 Getting close to a real fault simulation  Modern protective relays implement special algorithms to enhance the relay operating time in zone 1.  A trip time below 1 cycle is required for EEHA lines.  To work properly, the currents seen by the relay must have a smooth change from pre-fault to fault Good simulationBad simulation

Frankfurt (Germany), 6-9 June 2011 The DC offset  It is not easy to have this simulation at any time  It requires the software or hardware to evaluate this equation at every transition  Where I 1 = RMS value of the fault current I 0 = instantaneous value of the current just before the fault = Time constant t = Time in seconds, fault occurs at t=0

Frankfurt (Germany), 6-9 June 2011 This can be done with Comtrade files ?  It is a strategy to perform a single shot test, but...  A total of 6 channels With fault duration of 1.2 s sampled at 1 kHz 2 bytes per sample  Requires a file of 720 kB to be uploaded  With a 10 Mbps or 100 Mbps this can be uploaded very quickly, therefore it might not be a problem

Frankfurt (Germany), 6-9 June 2011 But what about developing faults ?  A developing fault is a sequence of states where every state depends on what happened in the previous state  Due to this, a Comtrade has the limitation that the exact time of transition between states is not certain  The exact time of transition determines the DC offset of the currents in the following state

Frankfurt (Germany), 6-9 June 2011 The DC offset calculated on the fly  Due to this, the DC offset must be evaluated by the hardware itself  The firmware of the equipment must be able to elaborate, at high speed, this formula  Since the sampling rate of the genaration must be kept relatively high, 10 to 20 kHz, for all current involved in the test

Frankfurt (Germany), 6-9 June 2011  Failing to do that, a simulation like the following would become impossible A simulation like thisWill appear like this

Frankfurt (Germany), 6-9 June 2011 Conclusion for part 2  Nowaday, testing a relay is not simply a characteristic check  Smarter relays require smarter test equipments  Smarter test equipment require high speed dedicated processors  We have answers to all testing problems may arise in the field.

Frankfurt (Germany), 6-9 June 2011 Thanks very much for your attention Mauro Borrielli Doble engineering company Client support engineer Web: