MEDIUM VOLTAGE CABLE

N2XSEY – YJV (CU/XLPE/CTS/PVC) IEC 60502-2

N2XSEY – YJV is a three-core medium voltage power cable with compacted copper conductors, XLPE insulation between semi-conducting screens, a copper tape screen on each core and a PVC sheath, built in accordance with IEC 60502-2 for rated voltages from 3.6/6 (7.2) kV to 18/30 (36) kV. In the German-style code, 2X denotes XLPE insulation, SE a copper screen over each individual core and Y the PVC sheath, while the absence of the letter A indicates copper; YJV is the Chinese type code. It serves distribution and plant supply networks.

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N2XSEY – YJV has three individually screened cores laid up together under one PVC sheath. On each core, two extruded semi-conducting layers confine the electrical field within the XLPE insulation, and a copper tape screen over the insulation screen forms the earthed metallic layer of that core. The three core screens touch each other along the cable, and non-hygroscopic fillers and a binder keep the assembly round. The XLPE insulation allows a conductor temperature of 90 °C in normal operation and 250 °C during a short circuit.

Cable Construction

Conductor: Annealed copper, Class 2 stranded and compacted circular, as defined in IEC 60228; the standard permits measures for longitudinal watertightness in Class 2 conductors (IEC 60502-2 Clause 5).
Conductor screen: Extruded semi-conducting compound applied over the conductor (IEC 60502-2 Clauses 7.1 and 7.2).
Insulation: Extruded XLPE, with nominal thickness selected by rated voltage and cross-section from IEC 60502-2 Table 6; the thickness of the semi-conducting screens is not included (IEC 60502-2 Clause 6.2).
Insulation screen: Semi-conducting compound extruded directly onto the insulation, of either the bonded or the strippable type (IEC 60502-2 Clause 7.3).
Metallic screen: Copper tape over the insulation screen of each core, non-magnetic as required for the individual cores of three-core cables, with the screens of the three cores in contact with each other; dimensions to national regulations and/or standards (IEC 60502-2 Clauses 8.4, 9, 10.1 and 10.2).
Assembly: Three screened cores laid up with non-hygroscopic fillers and a binder; with no collective metal layer, a separate inner covering may be omitted as long as the cable stays practically circular (IEC 60502-2 Clauses 8.2 and 8.4).
Outer sheath: Extruded PVC compound type ST2, the PVC grade rated for 90 °C (Table 4), black as standard; nominal thickness 0.035D + 1.0 mm and not less than 1.8 mm for multicore cables (IEC 60502-2 Clauses 14.1 to 14.3).

Rated Voltages and Insulation

Rated Voltage U0/U (Um)	Nominal XLPE Insulation Thickness	Cross-Sections in TDS
3.6/6 (7.2) kV	2.5 mm up to 185 mm², rising to 3.2 mm at 500 mm² and 630 mm²	3×25 mm² to 3×630 mm²
6/10 (12) kV	3.4 mm	3×25 mm² to 3×630 mm²
8.7/15 (17.5) kV	4.5 mm	3×25 mm² to 3×630 mm²
12/20 (24) kV	5.5 mm	3×35 mm² to 3×630 mm²
18/30 (36) kV	8.0 mm	3×50 mm² to 3×630 mm²

Choose the U0 rating from both the system voltage and the way the system clears earth faults. IEC 60502-2 Table 1 groups systems into Categories A, B and C; on a 17.5 kV system, for instance, 8.7/15 kV cable serves Categories A and B, whereas Category C calls for 12/20 kV cable. Overall diameters and weights in the TDS tab are approximate values that vary with the screen and filler design; insulation and sheath thicknesses are nominal values.

Typical Applications

Medium voltage distribution networks
Connection of generating units to the network
Power supply to industrial plants and process equipment
Direct burial, cable ducts, and indoor or outdoor installation

N2XSEY – YJV is a screened three-core medium voltage cable with copper conductors, XLPE insulation, copper tape screen on each core and PVC oversheath, built to IEC 60502-2. The characteristics below follow the voltage, material, thickness and temperature requirements of that standard; per-size dimensions, weights and conductor resistances are given in the TDS tab.

Technical Characteristics

Applicable Standard	IEC 60502-2
Standard Scope	Extruded-insulation power cables for fixed installations at rated voltages from 6 kV (Um = 7.2 kV) up to 30 kV (Um = 36 kV)
Rated Voltage U0/U (Um)	3.6/6 (7.2), 6/10 (12), 8.7/15 (17.5), 12/20 (24) and 18/30 (36) kV
Number of Cores	3
Conductor	Annealed copper, Class 2 compacted circular to IEC 60228
Nominal Cross-Section Range	25 mm² to 630 mm²; smallest size depends on rated voltage
Conductor Resistance at 20 °C	Not exceeding the IEC 60228 maximum; TDS values follow IEC 60228 Table 2
Conductor Screen	Extruded semi-conducting compound
Insulation	XLPE, nominal thickness to IEC 60502-2 Table 6
Insulation Screen	Extruded semi-conducting compound
Metallic Screen	Copper tape on each core; core screens in contact
Outer Sheath	PVC (type ST2), black as standard; nominal thickness 0.035D + 1.0 mm, minimum 1.8 mm
Maximum Conductor Temperature, Normal Operation	90 °C
Maximum Conductor Temperature, Short Circuit	250 °C, for a duration of not more than 5 s
Installation	Direct burial, cable ducts, indoors and outdoors

Ordering Information

Please state the rated voltage U0/U (Um), the nominal conductor cross-section, the required metallic screen cross-section or short-circuit rating, the total length and length per drum, the sheath colour if other than black and whether a strippable insulation screen is required.

No. of Cores and Nominal Cross Section	Nominal Insulation Thickness	Nominal Sheath Thickness	Approx. Overall Diameter	Approx. Weight	Max. D.C. Resistance of Conductor at 20°C
mm²	mm	mm	mm	kg/km	Ω/km
3.6/6(7.2)kV
3×25	2.5	2.1	34.4	1624	0.727
3×35	2.5	2.2	36.8	1978	0.524
3×50	2.5	2.3	39.3	2409	0.387
3×70	2.5	2.4	43.2	3118	0.268
3×95	2.5	2.5	47.3	3988	0.193
3×120	2.5	2.6	50.1	4786	0.153
3×150	2.5	2.7	53.5	5708	0.124
3×185	2.5	2.8	57.4	6918	0.0991
3×240	2.6	3.0	63.2	8692	0.0754
3×300	2.8	3.2	69.2	10635	0.0601
3×400	3.0	3.5	76.5	13493	0.0470
3×500	3.2	3.7	85.2	16823	0.0366
3×630	3.2	3.9	93.6	21093	0.0283
6/10(12)kV
3×25	3.4	2.2	38.9	1835	0.727
3×35	3.4	2.3	41.3	2202	0.524
3×50	3.4	2.4	43.8	2645	0.387
3×70	3.4	2.5	47.7	3374	0.268
3×95	3.4	2.7	52.0	4287	0.193
3×120	3.4	2.8	54.8	5101	0.153
3×150	3.4	2.9	58.2	6041	0.124
3×185	3.4	3.0	62.1	7272	0.0991
3×240	3.4	3.2	67.5	9045	0.0754
3×300	3.4	3.3	72.4	10914	0.0601
3×400	3.4	3.5	78.7	13688	0.0470
3×500	3.4	3.7	86.5	16954	0.0366
3×630	3.4	4.0	95.1	21279	0.0283
8.7/15(17.5)kV
3×25	4.5	2.4	44.5	2150	0.727
3×35	4.5	2.5	46.9	2532	0.524
3×50	4.5	2.6	49.4	2998	0.387
3×70	4.5	2.7	53.3	3761	0.268
3×95	4.5	2.8	57.4	4685	0.193
3×120	4.5	2.9	60.2	5536	0.153
3×150	4.5	3.0	63.6	6500	0.124
3×185	4.5	3.2	67.7	7755	0.0991
3×240	4.5	3.3	72.9	9524	0.0754
3×300	4.5	3.5	78.0	11598	0.0601
3×400	4.5	3.7	84.2	14315	0.0470
3×500	4.5	3.9	92.1	17766	0.0366
3×630	4.5	4.1	100.5	22101	0.0283
12/20(24)kV
3×35	5.5	2.7	52.0	2855	0.524
3×50	5.5	2.8	54.6	3336	0.387
3×70	5.5	2.9	58.5	4121	0.268
3×95	5.5	3.0	62.5	5069	0.193
3×120	5.5	3.1	65.3	5937	0.153
3×150	5.5	3.2	68.8	6921	0.124
3×185	5.5	3.3	72.6	8169	0.0991
3×240	5.5	3.5	78.0	10000	0.0754
3×300	5.5	3.6	83.0	12068	0.0601
3×400	5.5	3.9	89.4	14858	0.0470
3×500	5.5	4.1	97.3	18355	0.0366
3×630	5.5	4.3	105.7	22739	0.0283
18/30(36)kV
3×50	8.0	3.1	66.0	4165	0.387
3×70	8.0	3.2	69.9	4997	0.268
3×95	8.0	3.4	74.1	6027	0.193
3×120	8.0	3.5	76.9	6932	0.153
3×150	8.0	3.6	80.4	7960	0.124
3×185	8.0	3.7	84.2	9257	0.0991
3×240	8.0	3.8	89.4	11117	0.0754
3×300	8.0	4.0	94.6	13288	0.0601
3×400	8.0	4.2	100.8	16118	0.0470
3×500	8.0	4.4	108.7	19712	0.0366
3×630	8.0	4.7	117.3	24250	0.0283

Electrical Tests

In accordance with IEC 60502-2 Clause 16.2, the d.c. resistance of each conductor is measured as a routine test, corrected to 20 °C and 1 km, and does not exceed the maximum value of IEC 60228 Table 2 for Class 2 copper conductors.
In accordance with IEC 60502-2 Clause 16.3, the routine partial discharge test to IEC 60885-3 is made on all three insulated cores, each between conductor and screen, raising the voltage to 2 U0 for 10 s and reducing it to 1.73 U0, at which no discharge above the declared sensitivity of 10 pC or better is detected.
In accordance with IEC 60502-2 Clauses 16.4.3 and 16.4.4 and Table 11, a power-frequency voltage of 3.5 U0 is applied for 5 min between each conductor and the metal layer as a routine test: 12.5, 21, 30.5, 42 and 63 kV for the five voltage ratings.
In accordance with IEC 60502-2 Clause 17.9, cables rated above 3.6/6 (7.2) kV withstand a 4 h power-frequency voltage test at 4 U0 as a sample test.
In accordance with IEC 60502-2 Clauses 18.2.4 and 18.2.5, a type test sample is wound round a test cylinder and unwound, alternating the bending direction, for three cycles, and then shows no discharge exceeding the declared test sensitivity of 5 pC or better at 1.73 U0.
In accordance with IEC 60502-2 Clauses 18.2.6 and 18.2.7, tan δ is measured for ratings of 6/10 (12) kV and above, and the sample completes 20 heating cycles at 5 K to 10 K above the maximum normal conductor temperature.
In accordance with IEC 60502-2 Clause 18.2.8 and Table 14, each core withstands 10 positive and 10 negative impulses at 60, 75, 95, 125 or 170 kV peak according to rating, followed by a power-frequency voltage test.

Mechanical Tests

In accordance with IEC 60502-2 Clause 19.5 and Table 17, XLPE insulation has a tensile strength of at least 12.5 N/mm² and an elongation at break of at least 200% before ageing, with a variation of no more than ±25% after 168 h at 135 °C.
In accordance with IEC 60502-2 Clauses 19.6 and 19.7, the ST2 PVC sheath meets the mechanical requirements of Table 20 before and after ageing, and pieces of completed cable are aged to confirm compatibility between components.
In accordance with IEC 60502-2 Clause 19.23, where the insulation screen is declared strippable, the force to remove it is between 4 N and 45 N before and after ageing, leaving no damage or residue on the insulation.

Physical and Material Tests

In accordance with IEC 60502-2 Clause 17.5, the smallest insulation thickness is at least 0.9 times nominal minus 0.1 mm, the eccentricity ratio (tmax − tmin)/tmax does not exceed 0.15, and the smallest sheath thickness is at least 0.8 times nominal minus 0.2 mm.
In accordance with IEC 60502-2 Clause 17.10 and Table 19, the XLPE hot set test at 200 °C under 20 N/cm² gives an elongation under load of not more than 175% and a permanent elongation of not more than 15%.
In accordance with IEC 60502-2 Clause 19.18 and Table 19, XLPE insulation shrinks by no more than 4% after 1 h at 130 °C.
In accordance with IEC 60502-2 Clauses 19.8 to 19.11, the ST2 PVC sheath passes the loss of mass test, the pressure test at high temperature, the low-temperature tests and the heat shock test.

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Selected Product: N2XSEY – YJV (CU/XLPE/CTS/PVC) IEC 60502-2