We can design it. We can build it. Alongside the standard product range, Straton Electricals builds custom-designed equipment — metering cubicles, isolation and control transformers, auxiliary transformers, and reference-grade standard transformers — matched to a customer’s exact winding ratio, accuracy class, mounting, and insulation requirement. Roughly 60% of what leaves the factory floor is a custom configuration rather than an off-the-shelf part.
Custom Make
Custom Products
We can design it. We can build it.
Engineering Capability
Custom Instrument Transformer Design Capabilities
Straton Electricals engineers custom current transformers and voltage transformers for applications where standard catalogue products don't meet system requirements. Our in-house design team works directly with utility engineers, EPC contractors, renewables (solar and wind), data centres and OEMs to develop instrument transformers to exact specifications — covering non-standard ratios, special burden ratings, dual-core configurations, and custom accuracy classes.
From cast resin designs compliant with DIN 42600 to oil-impregnated paper (OIP) insulated high voltage designs up to 245kV, each custom transformer undergoes the same rigorous testing as our standard range — including partial discharge testing, tan delta testing, ratio and polarity verification, and accuracy testing.
Standard Current Transformer
Reference-grade current transformers used to verify the accuracy of other CTs, typically in a laboratory or calibration environment where a stable, high-precision benchmark is required.
Maximum primary current10000 A
Secondary currents1 A, 5 A, and customer-specific
Max. secondary insulation3 kV standard, 5 kV on special order
Max. accuracy±0.005%
Max. phase angle±0.5 min
Measuring range1–200% of In
BurdenMax. 15 VA, or customer-specific
Operating frequency50–200 Hz
Insulation typeDry / air-cooled / cast resin
ConstructionBar primary or wound
TappingPrimary and secondary tapping available on request
Standard Voltage Transformer — HV
Reference-grade voltage transformers used to calibrate other VTs and confirm accuracy conformance within a measurement system.
Max. primary voltageUp to 220 kV / √3
Also available in132 / 110 / 66 kV / √3
Secondary voltages100 V, 110 V, 100/√3 V, 110/√3 V, and custom
Voltage factor1.9 × Un
Max. voltage accuracy±0.005%
Max. phase angle accuracy±0.5 min
Measuring range20–120% of Un
Measuring frequency50 & 60 Hz
Operating frequency50–150 Hz
InsulationOil impregnated paper (OIP)
ConfigurationSingle-phase
AC Test Transformer
Used for dielectric and routine testing of motors, generators, transformers and other electrical equipment, sized and configured for the specific test application.
Max. output voltage130 kV
Input voltage230 V / 400 V, or per customer requirement
Max. output5 kVA continuous, 10 kVA duty cycle (1 hr on / 23 hr off)
Tripping current50 mA
Operating frequency50 or 60 Hz
Weight~450 kg
Dimensions~650 × 650 × 1400 mm
Custom optionsPrimary/secondary tapping, mobile castor-mounted, PD-free, special frequencies, compact or cascade designs
Metering Cubicles / Panels
Steel-enclosed metering assemblies that house current transformers, voltage transformers and meters together for accurate, safe measurement of power distribution networks.
Rated voltage11 kV / 33 kV
Rated current1–2000 A
Accuracy class0.2S / 0.2 / 0.5 / 0.5S / 1.0
BurdenAs per customer or statutory requirement
Frequency50 Hz
InstallationIndoor / outdoor
ProvisionsOptional energy meter
Isolation / Control Transformer
Separates one circuit from another, blocking DC flow while transferring power via two windings arranged to cancel magnetic flux — common in medical equipment, power supplies and industrial automation.
Rating1 kVA – 25 kVA
Reference standardIS 11171:1985 (reaffirmed 2006)
ConfigurationDelta/Star or user-defined (1:1)
Default vector groupDyn11
Load regulationBetter than 3%
Insulation classH
Common-mode noise rejectionOver 100 dB up to 10 kHz
DC galvanic isolation> 500 MΩ
HousingSheet-metal enclosure with input/output terminals
Cast Resin Monoblock
A single-piece epoxy-resin bushing with an aluminium core component, used across medium- and high-voltage transformers as a durable, cost-effective secondary connection that also guards against oil leakage.
WiresTin-plated high-conductivity copper
Wire insulationPTFE
Terminal connectionsUp to 17
Insulation classH
Insulation level3 kV for 1 min.
Standard Voltage Transformer — MV
A medium-voltage reference transformer used to check the accuracy of other VTs during calibration and testing.
Max. primary voltageUp to 40 kV / √3
Secondary voltages100 V, 110 V, 100/√3 V, 110/√3 V, and custom
Voltage factor1.9 × Un
Max. voltage accuracy±0.01%
Max. phase angle accuracy±1 min
Measuring range60–120% of Un
Measuring frequency50 & 60 Hz
Operating frequency50–150 Hz
InsulationCast resin
ConfigurationSingle-phase
Weight / dimensions50 kg, 225 × 270 × 290 mm
Auxiliary Transformer
A dedicated auxiliary/control-power transformer sized for the customer's secondary voltage and load requirement.
Max. primary voltageUp to 60 kV
Secondary voltages100 V, 110 V, 100/√3 V, 110/√3 V, 100/3 V, 110/3 V, 230 V, and custom
Voltage factor1.9 × Un
Max. voltage accuracy±0.01%
Max. phase angle accuracy±1 min
Measuring range60–120% of Un
Operating frequency50–150 Hz
InsulationCast resin
ConfigurationTwo-phase
Weight / dimensions80 kg, 450 × 300 × 850 mm
FAQ
Frequently Asked Questions
A current or voltage transformer engineered to specifications beyond standard catalogue ratings — covering non-standard CT ratios, special burden values, dual-core designs, specific accuracy classes, or unique installation requirements. Straton Electricals designs and manufactures custom CTs and PTs from LV to 245kV for utility substations, industrial power systems, Data Centres and renewable (solar and wind) energy applications.
Straton Electricals manufactures custom instrument transformers across low voltage, medium voltage (up to 36kV), and high voltage (up to 245kV) classes. Each design is engineered to meet specific substation and transmission network requirements with customised CT ratio, burden, and accuracy class configurations.
Custom current transformers from Straton Electricals comply with IS 16227 (aligned with IEC 61869), and DIN 42600 for cast resin designs. Each transformer undergoes routine and type testing including partial discharge, tan delta, ratio, polarity, and insulation withstand tests.
To engineer a custom instrument transformer, Straton's team requires: system voltage, primary current or voltage, required CT ratio or PT ratio, accuracy class (metering or protection), burden rating (VA), installation type (indoor/outdoor), insulation type preference, and applicable standards.
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