Voltage sensors

More than 15 years of experience in medium voltage sensors

Three sensor technologies. Which one is yours?

All three cover medium voltage. What separates them is what the signal is for.

Ohmic Voltage Sensor [+], Indisol — Ohmic Voltage Sensor [+]

Ohmic Voltage sensor

Capacitive Voltage Sensor [+], Indisol — Capacitive Voltage Sensor [+]

Capacitive Voltage sensor

Resistive Capacitive Voltage Sensor [+], Indisol — Resistive Capacitive Voltage Sensor [+]

Medium voltage sensor - Resistive Capacitive Voltage sensor

A medium voltage sensor does the job of an instrument transformer with a voltage divider cast into epoxy: the same insulator that holds the conductor also delivers a low voltage image of what is on it. Indisol designs and manufactures them for 12 kV to 72 kV networks, in three divider technologies, with measured value deviation down to 0.2%.

Choosing between the three is not really a question of voltage — all three cover the medium voltage range. It is a question of what the signal has to do. A protection relay or a power quality analyser needs an accurate, linear image of the waveform. A voltage detecting system needs to know reliably whether the busbar is live. A hybrid does both from one part.

Because the divider is cast into the insulator, there is no saturable core anywhere in the part. That is the practical reason these sensors cannot fall into ferroresonance, and it is also why they are smaller and lighter than the transformer they replace instead of being one more component in the panel.

Every part is engineered to your interface rather than picked from a catalogue, so the housing, the height and diameter, the fixing centres and the secondary connector follow your switchgear.

Not sure which of the three you need? Send us the operating voltage, the accuracy class and what the signal feeds — a protection relay, a monitoring system, or voltage indication — and we will tell you which technology fits.

Medium voltage voltage sensors and a cast epoxy post insulator, Indisol

Range of cast epoxy medium voltage sensor insulators, Indisol

Ohmic voltage sensor as an end piece in a medium voltage plug set, Indisol

Medium voltage voltage indicator panel with capacitive coupling plugs, Indisol

Ohmic, capacitive and resistive-capacitive medium voltage sensors, cast in epoxy by Indisol

12–72 kVOperating voltage range

0.2%Best measured value deviation

3.25 VStandardised secondary output

3Divider technologies

What you get instead of an instrument transformer

Size and weight. A cast divider is a fraction of the volume of a wound transformer of the same rating, and it is the insulator as well — so it takes the place of a component rather than asking for space the panel does not have.

No ferroresonance. Ferroresonance needs a saturable magnetic core to resonate against the network capacitance. A divider has no core, so the failure mode is removed rather than damped.

Linearity and bandwidth. A wound transformer is designed around one frequency. A divider is linear by construction and holds its ratio across a wide frequency range, which is what makes harmonic and transient information usable.

Standardised interfaces. The ohmic range outputs 3.25 V through a pluggable BNC connector or an RJ45 interface, so integration with monitoring and control systems is a wiring job rather than an engineering project.

Where our sensors are used

The ranges are optimised for indoor applications. Three settings account for most of what we ship.

SwitchgearMeasurement and protectionVoltage measurement inside medium voltage switchgear assemblies, feeding protection relays, control and automation. This is where the space constraint is tightest and where a divider earns its place.

Transformers and distribution gridsMonitoring and fault locationContinuous monitoring, diagnostics, and fault detection and localisation. An accurate image of the line voltage is what lets you measure network conditions and work out where a fault came from.

Voltage detecting systemsVDS LRM and HRCapacitive insulators and coupling electrodes for LRM (low resistance) and HR (high resistance) voltage detecting systems, including retrofits on switchgear that is already in service.

How a sensor gets specified

Four things settle the design. You do not need all of them to start a conversation.

01Operating voltage12, 17, 24, 36, 45, 52 or 72 kV, depending on the technology. Tell us the system voltage and the insulation coordination you work to.

02Accuracy classMeasured value deviation of 0.2% or 0.5% on the ohmic range; classes from 1% down to 0.2% on the resistive-capacitive range.

03What the signal feedsA protection relay, a monitoring or power quality system, or a voltage detecting system. This is what decides between resistive, capacitive and hybrid.

04Interface and geometryWhether the part also has to support the conductor, the height and diameter available, and the secondary connector — BNC, RJ45 or connecting leads.

Compatibility and testing

The sensor design is mechanically and electrically compatible with widely used connector sets and components, including balanced plugs, Nexans, NKT, Südkabel and TE Connectivity. Tell us what you already have in the panel.

Testing runs in house and in external laboratories under ISO 9001 and ISO 14001: industrial frequency and partial discharges to 200 kV, high voltage and current metrology, and contact resistance.

Series parts are cast by gelation under pressure at temperature, which is what keeps the divider ratio and the dielectric behaviour consistent across a whole production run. More on how we cast them.

The rest of what we cast

A voltage sensor is one of seven families of cast epoxy parts. Go straight to the right one.

Support & post insulatorsHold a conductor away from earth and carry the mechanical load.See the range →

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.You are here

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 →

Common questions

What is the difference between a voltage sensor and a voltage transformer?A transformer measures voltage with an iron core and windings. A sensor measures it with a voltage divider cast into the insulator. The sensor is smaller and lighter, stays linear across a wide frequency range, and has no saturable core — so it cannot fall into ferroresonance.

How accurate are they?Measured value deviation of 0.2% or 0.5% on the ohmic range, and accuracy classes from 1% down to 0.2% on the resistive-capacitive range.

What comes out of the secondary side?On the ohmic sensors, 3.25 V — a standardised level for monitoring equipment — through a pluggable BNC connector or an RJ45 interface.

Can they be retrofitted into existing switchgear?Yes, and it is a common case. TSK capacitive insulators match the dimensions of conventional DIN insulators without coupling capacitance, so they work as direct replacements; KKE coupling electrodes cover retrofits where no mechanical support is needed; and custom dimensions are available for RCVS retrofit projects.

Indoor or outdoor?The sensor ranges are designed for indoor applications. If you need one outdoors, tell us the conditions — we cast outdoor insulators in a cycloaliphatic resin family and will tell you what is feasible.

Which technology should I ask for?Ohmic when you need the lowest deviation and a standardised measuring output. Capacitive when you need compact, cost-efficient voltage detection. Resistive-capacitive when you want accurate measurement and voltage presence indication from the same part.

Tell us what the signal has to do, and we will tell you which sensor to use.

Every part we cast is engineered to a specification rather than selected from a catalogue, so you 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 operating voltage — 12, 17, 24, 36, 45, 52 or 72 kVThe accuracy class you need, and what the signal feedsWhether the part also has to support the conductorThe secondary interface — BNC, RJ45 or connecting leadsHeight and diameter available, and whether this is a retrofit