Güral Elektrik Malzemeleri

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DISCONNECTORS

HV Disconnectors

Centre Break

Pantograph

Horizontal Break Pantograph
(knee type)

Indoor Earthing Switches

Outdoor Earthing Switches

Quick Make Earthing Switches

Operating Mechanisms

DC Disconnectors

for Railway Applications

Operating Mechanisms

Switch-Disconnectors

Outdoor Switch-Disconnectors

Indoor Switch-Disconnectors

Operating Mechanisms

Switch Disconnectors
Fuse Combinations

Indoor Switch Disconnector
Fuse Combinations

Operating Mechanisms

HV FUSES

Current Limiting Back-up Fuses

General

High voltage current limiting back-up fuses are system elements that are widely employed in HV systems to protect overhead lines, power cables, motors, transformers, capacitor banks, disconnectors and switches against circuit currents over rated values.

Güral MGM and MGN type back-up fuses are current limiting and high breaking capacity solutions for the
mentioned purposes, at any rated system voltage between 7.2kV and 36kV and for indoor or
outdoor applications.

Güral high voltage current limiting back-up fuses are available as three types in the market:

MGM type, fuse link with integrated “Medium” type (50N) striker mechanism,
MGM type, fuse link with integrated “Heavy” type (80N) striker mechanism,
MGN type, fuse link without any striker mechanisms.

Design and Performance

The construction schema of Güral high voltage current limiting back-up fuses are given below.
The fuse body (1)is of high quality brown glazed porcelain material and is type C120, as
discripted in relevant standard. The Ni / Ag plated contact heads (2) are plastered into the
chamfer on the body porcelain. The physical insulation of the fuse between these components
are maintained by special long endurance gaskets that are resistant to high temperatures.
The star shaped porcelain carrier (3) with the melting element banding (4) is assembled coaxially
in the body. The melting element is made of pure Ag, so as to maintain the lowest possible
cross section which is essential for the right operating of the fuse when needed. The melting element
is welded into both of the contact heads by a special technique. The remaing body volume is filled with
homogeneous quartz sand particles, which plays a critical role in breaking the current.The striker
mechanism is another part for MGM fuses (5). The striker is both a visiual sign of circuit breaking and
a mechanical power supply for some switch types triggered by striker sytems.

Superiorities of Güral High Voltage Back-up Fuses

Single design for indoor and outdoor applications.
Extreme breaking capacity.
Safe breaking of the critical current.
Safe breaking of the minimum breaking current.
Perfect cut – off characteristic.
Low power dissipation.
Pure Ag melting elements.
Robust and safe striker mechanism (available only for MGM type).
Low switching overvoltage.

Technical data and dimensions for GÜRAL's HV Fuse-Links types MGM and MGN

Rated voltage	Rated current	Dimensions		Rated breaking capacity	Minimum breaking current	Resistance	Power dissipation	Weight
Ur (kV)	Ir (A)	D (mm)	ØC1 (mm)	I`1` (kA)	I`3` = Imin (A)	Rcold (mW)	P (W)	W (kg)
7,2	2	292	53	25	8	414	3,5	1,6
	4				16	370	8,9
	6				28	144	5,8
	10				40	94	10,6
	16				68	54	16,5
	20				90	34	19
	25				110	27	23,6
	30				132	22,4	28,2
	40				170	16	45,2
	50		75		200	15	53,2	3
	63				240	10,2	60
	80				320	7	67,2
	100		84,5		400	4,6	69,6	4
	125				500	3,6	85,6
	150				600	3,1	105
	160				640	2,9	110
	200				800	2,5	150
	250				1000	1,8	212
12	2	292	53	25	8	822	5,9	1,6
	4				16	630	15,1
	6				28	240	9,7
	10				40	155	17,7
	16				68	90	27,6
	20				90	60	31,7
	25				110	50	39,3
	30				132	37	47
	40				170	27	75
	50		75		200	25	88,9	3
	63				240	17	100
	80				320	11,6	112
	100		84,5		400	8	116	4
	125				500	6,1	142
	150				600	5,2	174
	160				640	4,8	183
	200				800	4,2	250
17.5	2	442	53	25	8	1150	8,4	2,3
	4				16	910	21,6
	6				28	350	14,2
	10				40	228	25,8
	16				68	131	40,3
	20				90	83	46,2
	25				110	66	57,4
	30				132	54	68,5
	40				170	39	110
	50		75		200	36	129	4,5
	63				240	25	146
	80				320	17	163
	100		84,5		400	11,3	169	6
	125				500	8,9	208
	150				600	7,6	254
	160				640	7	267
	200				800	4,7	280
24	2	442	53	25	8	1570	11,8	2,3
	4				16	1260	30
	6				28	440	19,5
	10				40	315	35,4
	16				68	180	55,2
	20				90	113	63,4
	25				110	90	78,7
	30				132	75	94,1
	40				170	53	151
	50		75		200	50	179	4,5
	63				240	34	202
	80				320	23,3	224
	100		84,5		400	15,4	232	6
	125				500	12,3	285
	150				600	10,4	348
	160				640	9,6	366
	200				800	5,5	395
36	2	537	53	25	8	2300	17,4	2,8
	4				16	1120	44,9
	6				28	740	29,2
	10				40	450	53,1
	16				68	265	82,9
	20				90	170	95,2
	25				110	154	118,1
	30				132	103	141,1
	40				170	90	226
	50		75		200	75	268	5,1
	63				240	49	304
	80				320	35	336
	100		84,5		400	23,2	348	7
	125				500	18,4	428
	150				600	10,4	460
	160				640	10,6	465
	200				800	11,1	522

Characteristic Curves

TIME/CURRENT CHARACTERISTICS OF GÜRAL BACK-UP FUSES

CUT -OFF CHARACTERISTICS OF GÜRAL BACK-UP FUSES

I²t CHARACTERISTICS OF GURAL BACK-UP FUSES

STRIKER FORCE CHARACTERISTICS OF GÜRAL BACK-UP FUSES

Fuse Selection

Following criteria are important in the selection of fuses:
• The rated voltage of the fuse must be equal or higher than the rated system voltage.
If;
The operating voltage is higher than the rated voltage of the fuse:
- Inflammation during melting increases
- Thermal stresses on the fuse increases
- Value of the minimum breaking current of the fuse decreases
If;
The operating voltage is lower than the rated voltage of the fuse:
- Value of the minimum breaking current of the fuse increases
- Stresses during melting increases
• The rated maximum breaking current of the fuse must be egual or higher than the maximum three phase short-circuit current of the system.
• The rated current of the fuse should be higher than the permitted maximum load current of the circuit or equipment protected by the fuse but lower than the continuous current allowed by the thermal criteria for the protected circuit.
• Phase to earth fault current possible in the medium voltage network should be higher than the rated minimum breaking current of the fuse.

Transformer Protection

Following conditions must be fulfilled for protection of transformers:
• The fuse must be able to withstand the inrush magnetizing current of the transformer. It is calculated that the melting current of the fuse at 0.1 second must be higher than 10-12 times the rated current of the transformer.If (0.1 sec.) > (10-12) x In Transformer
•The fuse must be capable of breaking the fault current at the secondary terminals of the transformer.The fuse protecting the transformer must break before the foresighted short circuit current damages the transformer.
• The fuse must be able to withstand the continious service current as well as the eventual overloads.In order to get this, the rated current of the fuse must be higher than at least 1.3 times the rated current of the transformer.1.3 In trf < In Fuse An additional criteria for selection of fuses for the protection of distribution transformers is as follows:
When a short circuit occurs at the low voltage side of the transformer the associated short circuit current should be interrupted by protection equipment at the low voltage side of the transformer, if this is not possible the high voltage fuse at the primary side should melt. To fulfill this condition, the system should be designed such that in case of a short circuit at the low voltage side the short circuit current at the primary side of the transformer should be able to melt the fuse. In this case the current-time characteristics of the high voltage fuse should be considered. The current-time characteristics of the high voltage fuse should be higher than the current-time characteristics of the protection equipment at the low voltage side and the two protection systems should be coordinated.

Data Required for the Design of a Protection System for a Transformer of a Certain Rating :
1- Transformer characteristics
• Power kVA
• Short circuit voltage (Uk %)
• Rated Current
2- Fuse Characteristics
• Time-Current Characteristics
• Rated minimum breaking current I3
3- System and Operating Conditions
• Open air or air insulated cubicles or SF6 gas insulated cubicles etc...
• Continuous or not continuous overloads

FUSE SELECTION TABLE FOR DISTRIBUTION TRANSFORMERS
Transformator Characteristics								Güral MGM / MGN Fuse Selection
Rated Power	Rated Voltage	Rated Short-circuit voltage	Rated Duration of Thermic Withstand	Rated Current	30% overload current	Magnetising Current	Rated Short-Circuit Current	Minimum breaking current	Selected Fuse
kVA	kV	%Uk (%)	sec	Irt (A)	A	Ie (A / 0.1sec)	Ikt (A)	I`3` (A)
25	6,3 / 0,4	4	2	2,29	2,98	27,49	57,28	28	6A	7.2kV	36cm	25kA
25	10,5 / 0,4	4	2	1,37	1,79	16,50	34,37	16	4A	12kV	36cm	25kA
25	15,8 / 0,4	4	2	0,91	1,19	10,96	22,84	16	4A	17.5kV	51cm	25kA
25	20 / 0,4	4	2	0,72	0,94	8,66	18,04	16	4A	24kV	51cm	25kA
25	33 / 0,4	4,5	2	0,44	0,57	5,25	9,72	8	2A	36kV	61cm	25kA
50	6,3 / 0,4	4	2	4,58	5,96	54,99	114,56	40	10A	7.2kV	36cm	25kA
50	10,5 / 0,4	4	2	2,75	3,57	32,99	68,73	28	6A	12kV	36cm	25kA
50	15,8 / 0,4	4	2	1,83	2,38	21,93	45,68	28	6A	17.5kV	51cm	25kA
50	20 / 0,4	4	2	1,44	1,88	17,32	36,09	28	6A	24kV	51cm	25kA
50	33 / 0,4	4,5	2	0,87	1,14	10,50	19,44	16	4A	36kV	61cm	25kA
100	6,3 / 0,4	4	2	9,16	11,91	109,97	229,11	68	16A	7.2kV	36cm	25kA
100	10,5 / 0,4	4	2	5,50	7,15	65,98	137,47	68	16A	12kV	36cm	25kA
100	15,8 / 0,4	4	2	3,65	4,75	43,85	91,36	28	6A	17.5kV	51cm	25kA
100	20 / 0,4	4	2	2,89	3,75	34,64	72,17	28	6A	24kV	51cm	25kA
100	33 / 0,4	4,5	2	1,75	2,27	21,00	38,88	28	6A	36kV	61cm	25kA
125	6,3 / 0,4	4	2	11,46	14,89	137,47	286,39	90	20A	7.2kV	36cm	25kA
125	10,5 / 0,4	4	2	6,87	8,94	82,48	171,84	68	16A	12kV	36cm	25kA
125	15,8 / 0,4	4	2	4,57	5,94	54,81	114,19	40	10A	17.5kV	51cm	25kA
125	20 / 0,4	4	2	3,61	4,69	43,30	90,21	40	10A	24kV	51cm	25kA
125	33 / 0,4	4,5	2	2,19	2,84	26,24	48,60	28	6A	36kV	61cm	25kA
160	6,3 / 0,4	4	2	14,66	19,06	175,96	366,58	110	25A	7.2kV	36cm	25kA
160	10,5 / 0,4	4	2	8,80	11,44	105,58	219,95	68	16A	12kV	36cm	25kA
160	15,8 / 0,4	4	2	5,85	7,60	70,16	146,17	68	16A	17.5kV	51cm	25kA
160	20 / 0,4	4	2	4,62	6,00	55,43	115,47	40	10A	24kV	51cm	25kA
160	33 / 0,4	4,5	2	2,80	3,64	33,59	62,21	28	6A	36kV	61cm	25kA
200	6,3 / 0,4	4	2	18,33	23,83	219,95	458,23	132	30A	7.2kV	36cm	25kA
200	10,5 / 0,4	4	2	11,00	14,30	131,97	274,94	90	20A	12kV	36cm	25kA
200	15,8 / 0,4	4	2	7,31	9,50	87,70	182,71	68	16A	17.5kV	51cm	25kA
200	20 / 0,4	4	2	5,77	7,51	69,28	144,34	40	10A	24kV	51cm	25kA
200	33 / 0,4	4,5	2	3,50	4,55	41,99	77,76	28	6A	36kV	61cm	25kA
250	6,3 / 0,4	4	2	22,91	29,78	274,94	572,78	170	40A	7.2kV	36cm	25kA
250	10,5 / 0,4	4	2	13,75	17,87	164,96	343,67	110	25A	12kV	36cm	25kA
250	15,8 / 0,4	4	2	9,14	11,88	109,63	228,39	68	16A	17.5kV	51cm	25kA
250	20 / 0,4	4	2	7,22	9,38	86,61	180,43	68	16A	24kV	51cm	25kA
250	33 / 0,4	4,5	2	4,37	5,69	52,49	97,20	40	10A	36kV	61cm	25kA
315	6,3 / 0,4	4	2	28,87	37,53	346,42	721,71	240	63A	7.2kV	36cm	25kA
315	10,5 / 0,4	4	2	17,32	22,52	207,85	433,03	132	30A	12kV	36cm	25kA
315	15,8 / 0,4	4	2	11,51	14,96	138,13	287,77	90	20A	17.5kV	51cm	25kA
315	20 / 0,4	4	2	9,09	14,96	109,12	227,34	90	20A	24kV	51cm	25kA
315	33 / 0,4	4,5	2	5,51	7,16	66,13	122,47	68	16A	36kV	61cm	25kA
400	6,3 / 0,4	4	2	36,66	47,66	439,90	916,46	320	80A	7.2kV	36cm	25kA
400	10,5 / 0,4	4	2	21,99	28,59	263,94	549,87	170	40A	12kV	36cm	25kA
400	15,8 / 0,4	4	2	14,62	19,00	175,40	365,42	110	25A	17.5kV	51cm	25kA
400	20 / 0,4	4	2	11,55	15,01	138,57	288,68	90	20A	24kV	51cm	25kA
400	33 / 0,4	4,5	2	7,00	9,10	83,98	155,52	68	16A	36kV	61cm	25kA
500	6,3 / 0,4	4	2	45,82	59,57	549,87	1145,57	400	100A	7.2kV	36cm	25kA
500	10,5 / 0,4	4	2	27,49	35,74	329,92	687,34	200	50A	12kV	36cm	25kA
500	15,8 / 0,4	4	2	18,27	23,75	219,25	456,78	132	30A	17.5kV	51cm	25kA
500	20 / 0,4	4	2	14,43	18,76	173,21	360,85	110	25A	24kV	51cm	25kA
500	33 / 0,4	4,5	2	8,75	11,37	104,98	194,40	68	16A	36kV	61cm	25kA
630	6,3 / 0,4	4	2	57,74	75,06	692,84	1443,42	400	100A	7.2kV	36cm	25kA
630	10,5 / 0,4	4	2	34,64	45,03	415,70	866,05	240	63A	12kV	36cm	25kA
630	15,8 / 0,4	4	2	23,02	29,93	276,26	575,54	170	40A	17.5kV	51cm	25kA
630	20 / 0,4	4	2	18,19	23,64	218,24	454,68	132	30A	24kV	51cm	25kA
630	33 / 0,4	4,5	2	11,02	14,33	132,27	244,94	90	20A	7.2kV	61cm	25kA
800	6,3 / 0,4	6	3	73,32	95,31	879,80	1221,94	500	125A	12kV	36cm	25kA
800	10,5 / 0,4	6	3	43,99	57,19	527,88	733,16	320	80A	17.5kV	36cm	25kA
800	15,8 / 0,4	6	3	29,23	38,00	350,81	487,23	240	63A	36kV	51cm	25kA
800	20 / 0,4	6	3	23,09	30,02	277,14	384,91	200	50A	24kV	51cm	25kA
800	33 / 0,4	6	3	14,00	18,20	167,96	233,28	110	25A	36kV	61cm	25kA
1000	6,3 / 0,4	6	3	91,65	119,14	1099,75	1527,43	600	150A	7.2kV	36cm	25kA
1000	10,5 / 0,4	6	3	54,99	71,48	659,85	916,46	400	100A	12kV	36cm	25kA
1000	15,8 / 0,4	6	3	36,54	47,50	438,51	609,04	320	80A	17.5kV	51cm	25kA
1000	20 / 0,4	6	3	28,87	37,53	346,42	481,14	240	63A	24kV	51cm	25kA
1000	33 / 0,4	6	3	17,50	22,74	209,95	291,60	132	30A	36kV	61cm	25kA
1250	6,3 / 0,4	6	3	114,56	148,92	1374,68	1909,28	640	160A	7.2kV	36cm	25kA
1250	10,5 / 0,4	6	3	68,73	89,35	824,81	1145,57	500	125A	12kV	36cm	25kA
1250	15,8 / 0,4	6	3	45,68	59,38	548,13	761,30	400	100A	17.5kV	51cm	25kA
1250	20 / 0,4	6	3	36,09	46,91	433,03	601,42	300	75A	24kV	51cm	25kA
1250	33 / 0,4	6	3	21,87	28,43	262,44	364,50	170	40A	36kV	61cm	25kA
1600	6,3 / 0,4	6	3	146,63	190,62	1759,60	2443,88	1000	250A	7.2kV	36cm	25kA
1600	10,5 / 0,4	6	3	87,98	114,37	1055,76	1466,33	600	150A	12kV	36cm	25kA
1600	15,8 / 0,4	6	3	58,47	76,01	701,61	974,46	400	100A	17.5kV	51cm	25kA
1600	20 / 0,4	6	3	46,19	60,05	554,27	769,82	320	80A	24kV	51cm	25kA
1600	33 / 0,4	6	3	27,99	36,39	335,92	466,56	240	63A	36kV	61cm	25kA

Motor Circuit Protection

In general, the minimum breaking current need only be low enough to ensure correct coordination with the switching device over-current relay. Where additional safety is required, the fuse minimum breaking current should be at least as low as the stalled
rotor current of the protected motor. Back-up fuses are normally used for thisapplication
.
For direct-on-line applications, it is necessary to allow for the motor starting current which may typically be 6 times full load current for a period of several seconds. This point should be well to the left of the time-current curve for the fuse in question. Where start up is frequent, an additional allowance may need to be made to ensure against long term fuse deterioration.

The ability to withstand repetitive starting conditions is an important factor. When selecting a back-up fuse for a given motor circuit application, due regard should be paid to the K factor, which should be applied to the pre-arcing time-current characteristic of the fuse to take account of these starting conditions.

K factor: Factor which defines an overload characteristic to which the fuse may be repeatedly subjected under specified motor starting conditions, and other specified motor-operating overlaoads, without deterioration. For the purpose of this specification, the value of K is chosen at 10s.

.
Capacitor Protection

Where fuses are used to protect capacitor units, very low minimum breaking current values may be desirable in orter to take account of the small increases in current which occur when one or more capacitor elements break down. In the case of fuses
used only for line protection then fuses with an appropriately higher value of minimum braking current may be employed.

To select the correct fuse rating for a given application it is necessary to consider the harmonic content of the load current as well as the charging inrush current during switch-on.

WORKSHOP

Atatürk Sanayi Sitesi, Fahri Korutürk Caddesi, 323 Sokak, No:1, 34900
Hadımköy – ISTANBUL / TURKEY

Tel: +90 212 771 24 95-99 / 771 27 60-61 Fax: +90 212 771 27 62

OFFICE

Rıhtım Cadddesi, C Blok, No:59, Kat:2, Daire: 25, 34425
Karaköy – ISTANBUL / TURKEY

Tel: +90 212 249 82 80 Fax: +90 212 244 25 07

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