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Epoxy Support Insulators

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An epoxy support insulator holds a live conductor away from earth while carrying mechanical load at the same time. It keeps the energised parts of the equipment physically separated from the structure around them — which is what protects the installation, the people near it, and the continuity of service.

Indisol casts support and post insulators in epoxy resin, engineered to each application rather than picked from a catalogue: low, medium, high and very high voltage, indoors, outdoors, or in special environments such as SF6 and other dielectric fluids.

Because the part is cast rather than fired or machined, the geometry is yours to choose. Ribs, creepage profiles, mounting features and fixing centres are moulded in one piece, and threaded inserts or electrodes are encapsulated inside the resin instead of bolted on afterwards — no fasteners sitting in the insulating path.

Mechanical specification follows the duty: traction, bending or torsion. Mounting lashings follow the relevant standard or your own interface.

Looking for a different epoxy insulator? Bushings, GIS parts, dividers, sensors, third rail and custom housings are all cast here too — the guide below points you to the right one.

Range of cast epoxy support insulators, Indisol

Low voltage epoxy support insulators with threaded inserts, Indisol

Medium voltage epoxy post insulators, Indisol

Cast epoxy support and post insulators

20–40 kV/mmBreakdown strength of cast epoxy

LV to VHVVoltage classes we cast for

200 kVIn-house test ceiling

2 000 tEpoxy processed per year

Which epoxy insulator do you need?

“Epoxy insulator” is a family name, not a part number. A support insulator is one member of it. If the part you are specifying does something else, go straight to the right family.

Support & post insulatorsHold a conductor away from earth and carry the mechanical load.You are here

Medium voltage cast epoxy bushing, Indisol

BushingsTake a live conductor through a wall, an enclosure or a tank.See the range →

Cast epoxy components for gas insulated switchgear, Indisol

GIS productsBusbar supports, fuse tubes and breaker chambers inside gas insulated equipment.See the range →

Divider insulatorsInsulate and, at the same time, give a low voltage signal that follows the conductor.See the range →

Medium voltage voltage sensors and indicators in cast epoxy, Indisol

Medium voltage sensorsMeasure voltage or current to a stated accuracy class.See the range →

Epoxy insulator with integrated sensing for smart grids, Indisol

SmartGridSensing, monitoring and PLC communication built into the insulating part.See the range →

Third rail insulator supporting a T-section conductor rail, Indisol cast epoxy

Third rail insulatorsHold the conductor rail that powers a metro or light-rail line.See the range →

Customized cast epoxy product for medium and high voltage, Indisol

Custom HV/MV productsEpoxy housings for switches, and shapes none of the above describes.See the range →

Indoors or outdoors: the resin decides

This is the first thing we will ask you, and it is settled by where the insulator lives rather than by the voltage. Both families cover low, medium, high and very high voltage.

IndoorsAromatic epoxyBisphenol A-epichlorohydrin resin with an anhydride hardener. Excellent dielectric performance where the surface is protected from weather.

OutdoorsCycloaliphatic epoxyFilled with pre-treated silica. Resists UV, tracking and weathering without the surface degradation that limits general-purpose resins. Also the choice indoors where there is humidity or pollution.

Polluted or coastalCycloaliphatic, overmouldedThe same resin with a silicone layer overmoulded on our own line, adding surface protection where the environment is aggressive.

Where neither standard family suits the duty, resin systems can be developed to specific electrical, thermal and mechanical requirements. More on our epoxy resin technology.

How a support insulator is made

Most of what can go wrong electrically goes wrong during casting, which is why the process matters more than the datasheet.

01PrepareResin degassed under vacuum, so the mix reaches the mould without entrained air — the voids that would later become partial discharge sites.

02CastGelation under pressure at temperature for series work; vacuum or atmospheric casting for prototypes and small runs.

03FinishMetallization and sand blasting in our own factory, so the electrode and creepage surfaces stay under our control.

04ProveElectrical and mechanical testing in house and in external laboratories, under ISO 9001 and ISO 14001.

Specified to your duty, then tested

Cast epoxy has a breakdown strength of 20 to 40 kV/mm depending on the system. That is a material figure: it tells you the resin has a large margin, not the withstand voltage of a finished insulator. That also depends on the creepage path along the surface, the clearances through air and the field distribution around any embedded metal — so we dimension the part to your system voltage rather than calculating it from the material alone.

Mechanically, a support insulator usually carries load as well as voltage. Tell us the load and its direction — traction, compression, bending or torsion — and any deflection limit, and the section and fixings are designed to it. Mounting lashings follow the relevant standard or your own interface.

For gas insulated applications, where the electrical stress is highest, every single piece is tested rather than a sample: industrial frequency, partial discharges and X-ray examination of the casting.

ElectricalIndustrial frequency to 200 kVPartial discharges to 200 kVHigh voltage and current metrologyContact resistance

MechanicalFlexionTractionCompressionTwistImpactRoughness

The standard range

Nine families, from 1 kV terminal blocks to 72,5 kV long-creepage posts, all cast in epoxy resin and electrically tested. Pick the family by duty, then open it for every reference, with dimensions, creepage, thread sizes and weight.

FamilyDutyRatedkVFlexuralkNHeightmmCreepagemmIEC 60273designation44 refs

Block types H, B and TIndoor, busbar and terminal support12 – 425 – 5630 – 67—10 refs

Low-voltage blocks and short posts. Flexural strength varies by reference.

Reference	Type	RatedkV	FlexuralkN	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Shed ⌀mm (F)	Top thread(M)	Base thread(N)	Creepagemm	Weightkg
150100030	T-793	1	2	40	30	25	—	M6	M6	40	0,050
150100040	T-760	1	4	40	40	35	—	M10	M10	40	0,080
15012030	T-793 L25	1	2	25	29	26	—	M6	M6	30	0,040
150100010	H-35	1	2	35	20	20	30	M8	M8	36	0,035
150120010	H-35 MF	1	2	35	20	20	30	M8	M8	36	0,035
150100020	H-50	1	4	50	30	30	40	M10	M10	51	0,090
150120020	H-50 MF	1	4	50	30	30	40	M10	M10	51	0,090
150100050	T-120	1	2	55,7	40	35	—	M10	M8	66,5	0,100
150100060	B-45	1	2	45	24	24	34	M6	M6	60	0,035
150100070	B-50	1	2	50	22	22	34	M8	M8	65	0,060

Series T/RIndoor posts, 3 to 6 kV3 – 64 – 1640 – 6058 – 95—4 refs

Metallic insert size and location may be modified.

Reference	Type	RatedkV	FlexuralkN	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Basemm (D)	Top thread(M)	Base thread(N)	Creepagemm	Weightkg
150100080	T-500/R	3	4	40	50	50	36	M8	M8	58	0,120
150100090	T-1000/R	6	4	60	65	60	36	M12	M12	92	0,300
150100100	T-2000/R	6	8	60	90	85	60	M16	M16	92	0,600
150100110	T-5000/R	6	16	60	125	125	80	M20	M16	95	1,400

Series SOIndoor, conical body3 – 12880 – 13080 – 130—2 refs

Flexural strength 8 kN (8 000 N) across the family.

	Reference	Type	RatedkV	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Top thread(M)	Base thread(N)	Creepagemm	Weightkg
	150100290	SO-3	3	80	75	55	M16	M16	80	0,350
	150100292	SO-10	12	130	75	55	M16	M16	130	0,750

Series 400Indoor posts, medium voltage7,5 – 36495 – 310155 – 398JO 4 60 … JO 4 1709 refs

Flexural strength 4 kN (4 000 N) across the family. Top insert M16, base insert M12 on every reference.

Reference	Type	IEC 60273	RatedkV	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Creepagemm	Shedsn.º	Weightkg
150100125	AE-7,5 S4	JO 4 60	7,5	95	51	53	155	4	0,400
150100130	AE-10/12 S4	—	10	120	57	53	170	4	0,500
150100140	AE-20 Red S4	JO 4 75	12	130	58	53	184	4	0,600
150100150	AE-17,5/20 S4	JO 4 95	17,5	175	60	52	246	7	0,700
150100160	AE-20/24 S4	JO 4 125	24	210	65	52	254	7	0,900
150120160	AE-20/24 S4 L225	JO 4 125	24	225	65	52	269	7	1,000
150100170	AE-36 Red S4	JO 4 145	27	270	70	60	362	7	1,500
150100180	AE-30/36 S4	JO 4 170	36	300	74	61	388	7	1,600
150100190	AE-36/36 S4 L310	JO 4 170	36	310	74	61	398	7	1,700

Series 800Indoor posts, higher mechanical load10 – 528120 – 420218 – 690JO 8 75 … JO 8 1708 refs

Flexural strength 8 kN (8 000 N) across the family.

Reference	Type	IEC 60273	RatedkV	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Creepagemm	Shedsn.º	Top thread(M)	Base thread(N)	Weightkg
150100192	AE-10/12 S8	—	10	120	59	71	218	5	M20	M16	0,700
150100196	AE-20 Red S8	JO 8 75	12	130	60	71	228	5	M20	M16	0,750
150100202	AE-17,5/20 S8	JO 8 95	17,5	175	67	71	466	10	M20	M16	1,250
150100200	AE-20/24 S8	JO 8 125	24	210	70	71	501	10	M20	M16	1,600
150100212	AE-36 Red S8	JO 8 145	27	270	75	70	584	15	M20	M16	2,000
150100210	AE-30/36 S8	JO 8 170	36	300	75	70	690	15	M24	M16	2,200
150100220	AE-45 S8	—	45	350	96	105	640	12	M24	M16	4,500
150100230	AE-52 S8	—	52	420	115	70	650	14	M24	M16	4,200

Series AEIIndoor, longer leakage line12 – 308130 – 280385 – 627JO 8 753 refs

Flexural strength 8 kN (8 000 N). Top insert M20, base insert M16.

Reference	Type	IEC 60273	RatedkV	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Shed ⌀mm (F)	Creepagemm	Weightkg
150100250	AEI-10	JO 8 75	12	130	72	72	100	385	0,900
150100260	AEI-20	—	24	210	70	70	100	580	2,600
150100270	AEI-30	—	30	280	80	80	170	627	4,100

Series EIRIndoor, high mechanical load3016300770JO 16 1701 ref

Flexural strength 16 kN (16 000 N). Top insert M24, base insert M16.

	Reference	Type	IEC 60273	RatedkV	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Shed ⌀mm (F)	Creepagemm	Weightkg
	150100280	EIR-30	JO 16 170	30	300	110	110	150	770	5,600

Series AERIndoor, long leakage line, up to 72,5 kV20 – 72,54 – 8210 – 620388 – 1 295—3 refs

Flexural strength varies by reference.

Reference	Type	RatedkV	FlexuralkN	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Creepagemm	Shedsn.º	Top thread(M)	Base thread(N)	Weightkg
150100238	AER-20	20	4	210	105	60	388	7	M16	M10	1,500
150100239	AER-30	30	4	300	130	85	647	10	M16	M10	3,250
150100239	AER-72,5	72,5	8	620	200	120	1 295	15	M24	M16	16,000

Series AETCapacitive, for voltage measurement12 – 364130 – 300228 – 690JO 4 75 … JO 4 1704 refs

Capacitive insulators. Top insert M16, base insert M12, with M5 measuring tap.

Reference	Type	IEC 60273	RatedkV	Heightmm (A)	Body⌀ mm (B)	Flange⌀ mm (C)	Creepagemm	Weightkg
150100390	AET-12 kV	JO 4 75	12	130	60	71	228	0,700
150100395	AET-17,5 kV	JO 4 95	17,5	175	67	71	466	1,300
150100400	AET-24 kV	JO 4 125	24	210	70	71	501	1,600
150100410	AET-36 kV	JO 4 170	36	300	75	70	690	2,200

Dimensions and weights are catalogue values for the standard range; the drawing letters (A, ⌀B, ⌀C, D, F, M, N) are the marks used on our dimensioned drawings. Thread pitches follow UNE 21-110-83 (2) and IEC 60273 and can be changed to DIN 48136 on request; insert size and position can be modified. Need a voltage, a load or a height that is not in the range? We cast to drawing — send us the duty and we come back with a proposal.

Common questions

Can you work from our drawing?Yes. Every part we cast is engineered to the customer’s specification rather than picked from a fixed catalogue, so a drawing or a sketch of the interfaces is the most useful thing you can send.

Can metal parts be cast into the insulator?Yes — threaded inserts, electrodes and conductors are encapsulated in the resin, giving a monolithic part instead of an assembly.

Is a support insulator the same as a post insulator?In practice the terms are used interchangeably, and both describe the same job: separating conductors at different potentials while carrying mechanical load. You will also see them called standoffs.

Epoxy or porcelain?Porcelain remains a sound choice in many installations. Cast epoxy wins where you need a shape porcelain cannot easily give, where metal has to be encapsulated, or where weight and brittleness are a problem. We wrote a longer comparison of the two.

What voltages do you cover?Low, medium, high and very high voltage, in both resin families. Our in-house test capability reaches 200 kV for industrial frequency and partial discharges.

How big can the part be?From pieces above 50 kg and one metre down to small, intricate components, on 29 clamping machines and a continuous mixing line.

Send us the duty. We will design the insulator to it.

Every part we cast is engineered to a specification rather than selected from a catalogue, so you will get a design proposal back, not a page number. You do not need all of the detail to start.

Request a quotation → or see how we cast them

Useful to includeThe system voltage, and whether the insulator sits indoors, outdoors or in gasThe mechanical duty — load, direction, and any deflection limitFixing centres and interfaces, or a drawing if you have oneService temperature, and anything unusual about the environmentQuantity, and whether this is a prototype or a series