Electric Power Network Efficiency and Security (EPNES) 1 THE USE OF MICROMECHANICAL SWITCHES IN A POWER CIRCUIT BREAKER Esma Gel, Gerald T Heydt, Norma Faris Hubele, George G Karady, Arizona State University, Tempe, AZ, USA

Electric Power Network Efficiency and Security (EPNES) 2 Micro-switch based Circuit Breaker Concept

Electric Power Network Efficiency and Security (EPNES) 3 Conceptual circuit diagram for an ac circuit breaker Circuit breaker contains two switches Positive switch operates in the positive cycle Negative switch operates in the negative cycle

Electric Power Network Efficiency and Security (EPNES) 4 Switching string assembly with several strings connected in parallel. (Positive switch only ) lVoltage rating is increased by switching additional units in series lCurrent rating is increased by switching additional units in series

Electric Power Network Efficiency and Security (EPNES) 5 Switching string operation

Electric Power Network Efficiency and Security (EPNES) 6 Illustration of circuit breaker closing.

Electric Power Network Efficiency and Security (EPNES) 7 Illustration of current interruption.

Electric Power Network Efficiency and Security (EPNES) 8 Progress October February 2004 Karady

Electric Power Network Efficiency and Security (EPNES) 9 Proof of concept experiment

Electric Power Network Efficiency and Security (EPNES) 10 Reduced scale circuit breaker Control solenoid Switching string

Electric Power Network Efficiency and Security (EPNES) 11 The technical data of the developed small scale circuit breaker Rated current:8 A steady state Interruption current:50 A for a half cycle Rated voltage:4000 V BIL:95 kV Number of switches in series in a single string:10 Number of strings in parallel:8

Electric Power Network Efficiency and Security (EPNES) 12 Comparator checks whether current is above threshold If the current is above threshold, a signal is sent to latch a D Flip-Flop Turn off signal is sent to positive cycle switch if fault is initiated in positive cycle of line current. Turn-off signal is sent to the negative cycle switch soon after current zero. Automatic turn off

Electric Power Network Efficiency and Security (EPNES) 13 A positive pulse is sent to the latch using push button The output of the latch is sent to the positive and negative cycle logic blocks Turn-off signal is sent to the positive cycle switch if the switching is initiated in the positive cycle Turn off signal is sent to the negative cycle switch after current zero Manual turn off the switch

Electric Power Network Efficiency and Security (EPNES) 14 Using push button, a signal is sent to the positive and negative logic blocks to start/restart the circuit Logic blocks check for positive/negative cycle using voltage signal from source Turn on signal is sent to the positive cycle switch, if the turning on starts in positive cycle Turn on signal is sent to the negative cycle switch after current zero. Turn on the switch

Electric Power Network Efficiency and Security (EPNES) 15 Block diagram of the control circuit

Electric Power Network Efficiency and Security (EPNES) 16 PSpice simulation of the control circuit

Electric Power Network Efficiency and Security (EPNES) 17 Waveforms showing the working of the control circuit

Electric Power Network Efficiency and Security (EPNES) 18 Realization of MEMS base circuit breaker

Electric Power Network Efficiency and Security (EPNES) 19 lReceived 6 MEMS switches lDeveloped circuit diagram for operation of MEMS switches when operating coils are connected in series lDeveloped circuit diagram for operation of MEMS switches when operating coils are connected in parallel lDeveloped control concept

Electric Power Network Efficiency and Security (EPNES) 20 lMEMS Switch lRating: 100V, 100mA l Insulation 400V Positive coil current pulse close the switch Negative coil current pulse open the switch Operation requires: coil current of: 5V, 100mA

Electric Power Network Efficiency and Security (EPNES) 21 lNew latching type switch become available lThe switch has two position “ON” or “OFF” lThe switch has an operating coil lShort positive or negative pulse change switch position lThe problem is that the insulation has to withstand 7.2 kV between the contact and the magnet. Voltage: 400V Current : 100mA Resistance 0.5 ohm Insulation 400V Operating coil current: 100mA, 500 usec

Electric Power Network Efficiency and Security (EPNES) 22 lA diode and grading resistance is connected in parallel with the switch lThe switching coil is supplied by a microwave power supply lA antenna provided short duration 945Mz signal is rectified by the tunnel diode and capacitor lThe obtained DC signal operates the switch lThe 95kV BIL is achieved by a distance of 30 inches

Electric Power Network Efficiency and Security (EPNES) 23 Switching Unit Operation coils are connected in parallel

Electric Power Network Efficiency and Security (EPNES) 24 Switching Unit Realization

Electric Power Network Efficiency and Security (EPNES) 25 FUTURE WORK lFinalization the analytical technique for operation of large switching matrixes, l Improvement of reliability analysis and lTesting the proof of principle switching assembly. lDetailed design of the MEMS based switch lImplementation of the educational objective PROBLEM lNeed for 25 more switches lSurface mounting of MEMS switches