GE STD15C Instructions Manual Download

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Summary of Contents for STD15C

Page 1: ...GE K 45307K INSTRUCTIONS TRANSFORMER DIFFERENTIAL RELAYS WITH PERCENTAGE AN HARMONIC RESTRAINT TYPES STD15C and STD16C GE Protection and Control 205 Great Valley Parkway Malvern PA 19355 1337 ...

Page 2: ...haracteristics 12 BURDENS 13 CONSTRUCTION 14 Current Transformers 14 Through Current Restraint Circuit 14 Differential Current Circuit 15 Overcurrent Unit 15 Main Operating Unit 16 Target and Seal in Unit 16 Case 16 RECEIVING HANDLING AND STORAGE 17 ACCEPTANCE TESTS 17 Visual Inspection 17 Mechanical Inspection 17 Electrical Tests 17 Test Equipment 18 INSTALLATION PROCEDURE 18 Tests 18 Pickup 19 H...

Page 3: ...taps should be selected to obtain the maximum sensitivity without risking thermal overload of the relay or current transformer CT or the possibility of misoperation Therefore current transformer ratios in the various windings of the power transformer should be selected with the following points in mind 1 The lower the relay tap and the lower the CT ratio selected the higher will be the sensitivity...

Page 4: ...ided on the relay by means of which the currents may usually be matched within 5 When the protected transformer is equipped with load ratio control it is obvious that a close match cannot be obtained at all points of the ratio changing range In this case the secondary currents are matched at the middle of the range and the percentage_differential characteristic of the relay is relied upon to preve...

Page 5: ...rry the full self cooled rated kVA of the transformer or the equivalent self cooled ratings 100 Transformer kVA 100 P Line kV Actually this calculation does not mean that all windings will necessarily carry these maximum load currents continuously This is only a convenient way of calculating the currents in the other windings in proportion to their voltage ratings This is the requirement for selec...

Page 6: ...ansformer is less than 220 amperes RMS for 1 second If the period during which a fault current flows in the relay can be definitely limited to a shorter time a higher current can be accommodated in accordance with the relation Amperes x seconds 48 400 Also check that the suni of the multiples of tap current on an internal or external fault do not exceed 150 CURRENT TRANSFORMER RATIO ERROR The CT r...

Page 7: ... secondary current for 8 times tap setting 8 x STD relay tap rating Note For the location of fault assumed all the fault current is supplied by one CT so that CT current and relay current are the same regardless of whether the CTs are connected in wye or delta 3 Determine secondary CT voltage required at 8 times tap setting Esec IZ 4 From excitation curve of particular tap of current transformer b...

Page 8: ...MPLE REFER TO FIGURE 4 I Determination of CT Turns and STD Relay Tap Settings 1 Transformer and Line A B C 2 Maximum I 3750 J3 Line kV 19 7 49 5 157 3 100 Ip 3000 J Line kV 15 7 39 6 125 4 Assume CT turns N 20 20 60 5 Maximum I secondary less than 5a 0 98 2 47 2 62 6 100 I secondary 0 79 1 98 2 08 7 CT connections Delta Wye Delta 8 Relay Current for 100 I Sec 1 37 1 98 3 60 Select a relay tap for ...

Page 9: ...n 1 or Equation 2 from page 6 a Line A Z 2 0 156 20x4 2 0 x 75 1000 0 312 0 205 0 568 1 085 2 284 b Line 3 Z 0 096 20 x 2 5 2 0 x 52 5 1000 A T o85 25 6 27 8 1 00 3 4 0 568 B 0 8 36 8 29 4 50 136 C 0 833 69 6 58 0 0 5 0 8 Exciting current on line B is too high should improve CT performance IA Repeat CT Turns and Relay Tap Setting try higher tap on CT to 1 100 2 Try CT turns necessary to change C a...

Page 10: ...wice tap value if all but one of the restraint windings carry 0 current and the full restraint current equal to twice tap value flows through the differential current transformer Short Time Rating Thermal 220 amperes for 1 second measured in the primary of any transformer of the type STD relay Higher currents may be applied for shorter lengths of time in accordance with the following equation 48 4...

Page 11: ... normally used CHARACTERISTI Cs PICKUP AND OPERATING TIME The operating characteristic is shown in Figure 7 The curve for various percentage slopes shows the percent slope versus the throughcurrent flowing in the transformer The percentage slope is a figure given to a particular slope tap setting and indicates an approximate slope characteristic Pickup at zero restraint is approximately 30 of tap ...

Page 12: ...heir ratios to change with the result that the secondary currents become unbalanced Percentage restraint is also required to prevent operation by the unbalanced currents caused by imperfect matching of the secondary currents as previously described under Determination of CT Turns and STD Relay Tap Settings HARMONIC RESTRAINT CHARACTERISTICS At the time a power transformer is energized current is s...

Page 13: ...ult current waves is largely blocked by the auxiliary differential current transformer inside the relay and produces only a slight momentary restraining effect Relay operation occurs on differential current waves in which the ratio of harmonics to fundamental is lower than a given predetermined value for which the relay is set e g an internal fault current wave and is restrained on differential cu...

Page 14: ...is connected to stud 7 and the jumper normally connected between terminals 6 and 7 at the rear of the relay cradle should be disconnected at the terminal 6 end and reconnected to the upper row in the tap block above the row marked winding 1 which connects it directly to the differential current transformer in the STD relay The terminal on the movable lead should be placed under the tap screw that ...

Page 15: ...nt rectifier and can be adjusted to give the desired amount of harmonic restraint The output of the rectifier is paralleled with the through current restraint currents and applied to the restraint circuit of the sense amplifier It will be evident that if the differential current applied to the relay is sinusoidal and of system frequency it will flow mostly in the operating circuit and hence cause ...

Page 16: ...his unit will remain exposed until released by pushing a button beneath the lower left corner of the cover of the relay case CASE The case is suitable for surface or semi flush panel mounting and an assortment of hardware is provided for either method The cover attaches to the case and carries the target reset mechanism for the trip indicator and instantaneous unit Each cover screw has provision f...

Page 17: ...n their original cartons in a place that is free from moisture dust and metallic chips Foreign matter collected on the outside of the case may find its way inside when the cover is removed and cause trouble in the operation of the relay ACCEPTANCE TESTS Immediately upon receipt of the relay an inspection and acceptance test should be made to make sure that the relay has not been damaged in shipmen...

Page 18: ... amperes A source of DC power at rated voltage should be connected as shown in Figure 14 the indicating lamp will provide a signal showing that the main unit has operated For an additional pickup test the pickup should be 1 5 amperes with current flowing in terminals 5 and 6 and the tap plugs in the 5 ampere tap and the 25 slope tap position If the pickup is between 1 35 and 1 65 amperes no adjust...

Page 19: ...fy that the amplifier has produced an output signal Before Ri is adjusted for pickup put a DC voltmeter one volt scale on pin 2 and pin 8 of the sense amplifier card The pins are counted from right to left when viewed from the card socket wiring connections Apply pickup current and adjust Ri for a voltage input to the sense amplifier card of 0 430 to 0 470 volts If the pickup is not in limits with...

Page 20: ...ntial or percent slope characteristics is shown in Figure 7 It may be checked and adjusted using the circuit illustrated in Figure 15 with S2 closed to position B Ammeter I reads the differential current and 13 reads the smaller of the two through currents r CAUTION These currents should be permitted to flow for only a few seconds at a time with cooling periods between tests otherwise the coils wi...

Page 21: ...ATION The location should be clean and dry free from dust and excessive vibration and well lighted to facilitate inspection and testing MOUNTING The relay should be mounted on a vertical surface The outline and panel drilling dimensions are shown in Figure 18 CONNECTI ONS Internal connection diagrams are shown in Figures 10 and 11 Typical wiring diagrams are given in Figures 1 2 and 3 for differen...

Page 22: ...g the unbalance current flowing in the differential circuit without disturbing the relay connections Provision is made for temporarily connecting a 5 V high resistance AC voltmeter 1000 or more ohms per volt across the secondary of the differential current transformer This may be done by connecting the meter across terminals 8 and 9 see Figures 10 and 11 When a perfect match of relay currents is o...

Page 23: ...e units will operate depending upon the fault magnitude This will produce a target indication of the particular unit which operates After a fault is cleared the target should be reset by the reset slide located at the lower left hand corner of the relay DISABLING OF TYPE STD RELAY CAUTION When bypassing a breaker for maintenance it will be necessary to disable _ the relay to prevent false tripping...

Page 24: ...rip circuit through the test plug similar through jumpers should also be used on studs 8 and 9 to maintain the connections from the relay to the case If this is not done there is a risk of false tripping upon inserting or withdrawing the plug PICKUP The method for checking pickup is as described under the heading INSTALLATION TESTS except of course pickup current will be different depending upon t...

Page 25: ...based on a multiple of tap current of 6 times the lower tap setting for all combinations of taps except those which involve the 8 7 amp tap For the latter case a 4 times tap setting is used since the total test current for a 6 times tap setting may be as high as 75 2 amperes which is not only prohibitively high for many installations but also may subject the relay to excessive heating For a given ...

Page 26: ...e armature by hand The normally open contacts should make before the residual screw strikes the shim RENEWAL PARTS Sufficient quantities of renewal parts should be kept in stock for the prompt replacement of any that are worn broken or damaged When ordering renewal parts address the nearest Sales Office of the General Electric Company Specify the name of the part wanted quantity required and compl...

Page 27: ... 0 20 0 20 0 5 0 1l nin 4 5 7 5 12 0 20 3 23 8 29 0 1i max 5 0 8 3 13 2 20 9 24 7 30 5 13 34 8 34 8 34 8 8 7 J1 min 5 5 9 0 14 2 I1 niax 6 19 9 15 7 TABLE VIA frAPs T2 0 58 0 64 0 7 0 76 0 84 0 92 1 0 1 74 I Slopes 15 25 40 15 25 40 15 25 40 15 25 40 15 25 40 15 25 40 15 25 40 152iU T2 Currents 13 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 3 5 2 3 2 3 2 3 0 58 ...

Page 28: ...GEK 45307 IC 2 w P t frLL 2D 2 F LL ty S IlJIJ 2 0 i uJ 2 i u U o fr Figure 1 0128B1982 3 Elementary Diagram for STD16C Relays for Four Circuit Transformer Protection with Three Restraints 28 ...

Page 29: ...GEK 45307 74 WCaJ Figure 2 0128B1981 1 Elementary Diagram for STD15C Relays for Two Winding Transformer Protection I 2 w Ii U 1 I U _JI j I U I w 1 1 2 bi 0 I II I I I Fl 1 3C 4 r 29 ...

Page 30: ...U 0 GEK 45307 4 I Ln w ut Cr cr Cr 1L1 Ui w Figure 3 012881980 2 Elementary Diagram for STO 16C Relays for Three Winding Transformer Protection 3 U Cr 1 j 30 ...

Page 31: ...0165176O1 1 Figure 5 0227A2503_o Operating Speed Characteristics of the STD Relay I FKA 1500 46 Y w Al A FK 439 115 3000 KVA 3750 KVA 13 8 KV 600 5 FK 14 4 SELF COOLED FORCED AIR COOLED Transformer Used in Sample Calculations ELY IFF UTIA VIIF C T 31 ...

Page 32: ...AGE TAP LINKS HARMONIC RESTRAINT ADJUSTING RHEOSTAT 112 SLOPE ADJUSTING RHEOSTAT 113 Io MATCHING Figure 6A 8042539 Relay Type STD16C Out of Case Approximately 3 4 Front View Left Side REACTOR RECTIFIER CARD THYRITE RECTIFIER CARD TERMINAl IOARD I I REACTOR 12 P CAPACITOR C2 Figure 68 8042544 Relay Type STD16C Out of Case Approximately 3 4 Back View Right Side 32 ...

Page 33: ... IT IS TAKEN AS THE SUM OF THE NCG1ING OR OUTGOING CURRENTS WHICH EVER IS SMALLER EACH CURRENT TO BE EXPRESSED AS A MULTIPLE OF TAP 4 6 8 10 THROUGH CURRENT IN MULTIPLES OF TAP Figure 7A 0378A0588 3 Low Current Slope Characteristics of the STD Relay GEK 45307 80 10 1 LiJ 0 I Lii ii a Lii 1 EEEEEEEEEE 20__ _ 15 10 0 0 2 12 14 16 33 ...

Page 34: ...URRENT FOR THREE WINDING TRANSFOR MERS IT IS TAKEN AS THE SUM OF THE INCOMING OR OUTGOING CURRENTS WHICHEVE R IS SMALLER EACH CURRENT TO BE EXPRESSED AS A MULTIPLE OF TAR I r C S CD rz Ui 1 Ui 0 o C D W C I_S CD V CD S C CD c 0 CD S C CD S I q J C LI 11 I 100 90 80 M 70 P 60 R C E N 50 T S L 0 40 P E 30 20 I0 I jiI II 1 II m a LLLLL uh I 2 3 4 5 THROUGH CURRENT IN MULTIPLES OF TAP i Th ...

Page 35: ...re 8 K 6209195 O Fault Current and Transformer Magnetizing Current Waves Figure 9 0269A3039 3 Internal Connections Diagram of Sense Amplifier Printed Circuit Board I N13 Or I 7 I J a NOTE DY NEAR ICI CR UNLESS Al L RES J 2Wj5 OThERWISE ALL CAP VALUES IN MFj NOTED 2 TE4INL POINT DV P C CARD CO 4PON EN T5 TOP VIEW CI 35 ...

Page 36: ...R Figure 10 02571 5026 2 Internal Connections Diagram for Relay Type STD1SC THYRITE HARI4OflC DIFFERENTIAL OJRRENT TRANSFORIER RTR SENSE AMPLIFIER o257A5o57 THROUG OJRR RESTRAINT TRANSFOR4ER ECT 7i LEAD NO TO TXTNAI BOi 6 36 ...

Page 37: ... O257A5o27 1 I INST ThYRITE HARMONIC FR EQ RESTRAINT DIFFERENTIAL Cu RRENT TRANSFORMER SEllS E AMPLIFIER o257A 5057 t aiI TiT TO SHORT FINGERS 2 1 6 8 10 SHORT BRUSHES Internal Connections Diagram for Relay Type STD16C 37 ...

Page 38: ...S 4 INCH BEFORE ENGAGING THE MAIN BRUSH ON THE TERMINAL BLOCK Figure 12 8024039 Cross Section of Drawout Case Showing Position of Auxiliary Brush Figure 13 0148A2994 1 Outline of Test Rectifier CONNECTING BLOCK AUXILIARY BRUSH 1 TERMINAL BL SHORTING BAR O OF ARROW TE9IEeODY WI Fl 4RROW ON Ej_ 38 ...

Page 39: ...LED I TANTM4US OVEPaJRRENT UUT T SI TAT ND SEAL I 1 f S 1IO4E REI4Y GEK 45307 Figure 14 0165B2697 1 Test Connections Diagram TEST c4N FOP 5TW6C 39 ...

Page 40: ...ure 15 0257J5O54 o Sh 1 Field Test Connections in Case Using Type XLA Test Plug FREQUENCY S A TE5T CIRCUIT FOR STDI5C RELAYS AC I TEST RECTIFIFR I I AL DC 0148A2988 115 VOLTS RATED FREQUENCY LJ LOAD BOX RATED DC CO N T RCL VOLTS 2 LOAD OX INDICATING AC S4 LAMP i 40 ...

Page 41: ... DC set at 4 0 Amperes and By Pass Current Ij SLOPE 40 LL EE 44 4 _L 4 60 ThR0Uc1 CURRENT I N PERCENT OF TAP Figure 17 0178A8111 0 Differential Voltage Operating Characteristics of Type STD Relay 2 22 l c I I X 4 0 E 1 ZFEZZEE EEi LEH Is 1 3 4 5 6 LW PASS CURRLNT I IN A APiRE U U 10 50 70 90 100 41 ...

Page 42: ... 97531 00000 00000 10 8 6 4 2 H I 7 406 180MM L 5 187 131MM BACK VIEW CUTOUT MAY REPLACE DRILLED HOLES CU1IUT 14 912 375MM 3 500 5 8 DRILL 88MM 4 HOLES 4 156 15MM FIà5MM 8 31 1 211MMI 6 ___ __ 1 75Mj j 1 468 7I8 J I 18MM I 1 843 218 218 5MM 5MM 5 68 PANEL CASE 7 281 185MM FOR 6MM 5 25 133MM I 500 12MM TYPICAL 3 4 DRILL 10 HOLES 19MM 5 16 18 TYPICAL DIM 76MM INCHES VIEW SHOWING ASSEMBLY OF HARDWARE...

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Page 44: ...GE Power Management 215 Anderson Avenue Markham Ontario Canada L6E 1B3 Tel 905 294 6222 Fax 905 201 2098 www ge comlindsyslpm ...

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