Arteche Instrument Transformers: CA, UT, KA and Capacitive

Short answer

Arteche is a Spanish manufacturer of instrument transformers for high and extra-high voltage: CA series current transformers (up to 800 kV), UT series inductive voltage transformers, KA series combined current and voltage transformers (up to 245 kV) and capacitor voltage transformers. They are very common in substations and revenue metering points in Latin America.

What it is and where it is used

Arteche instrument transformers are found in a good share of the high-voltage substations and revenue metering points of Latin America. They are the Arteche CA current transformer, the UT voltage transformer and the KA combined unit. Arteche is a Spanish manufacturer with an industrial presence in the region. Besides instrument transformers, it makes reclosers, relays and automation equipment.

These units deliver to relays and meters a scaled-down replica of the system current and voltage. For the principle see high-voltage current transformer, inductive voltage transformer and capacitor voltage transformer.

Variants: Arteche CA, UT (UTD-123), KA-72, KA-245 and capacitor types

Model	Application	Main difference
CA (CA-123…)	Current, up to 800 kV	Top core, paper-oil, 1 to 5,000 A, up to 120 kA/1 s
UT (UTD-123…)	Inductive voltage	Metering and protection at high voltage
KA (KA-72, KA-245)	Combined current and voltage, up to 245 kV	One unit per phase, capacitive paper-oil bushing
Capacitor voltage transformers	Voltage at high and extra-high voltage	Capacitive divider, also useful for power line carrier
Medium voltage (indoor and outdoor)	Switchgear and distribution networks	Resin units for switchgear and poles

The exact designation and the data of each unit are on its nameplate. References of the same brand, such as the “Arteche UCL”, are identified by their nameplate and datasheet.

Main features

Top core in the CA series: the cores sit in the head of the unit and the primary is short, which favors short-circuit withstand.
Metering accuracy of up to class 0.1 in the CA series, and independent protection cores.
KA combined units to save space, structures and foundations.
Paper-oil insulation with porcelain or composite insulators depending on the version.

Communications and integration

An instrument transformer does not communicate: it delivers analog signals to the relay, the meter or a merging unit that digitizes them for IEC 61850. At revenue metering points, the metering core and the meter must meet the class required by the utility or the applicable metering code. See merging unit.

Current series: CA, CX and the others

Arteche’s website (in English and Spanish) organizes the high-voltage current transformers by series, and the design differences explain why they are not tested or specified in the same way:

Series	What Arteche publishes	Where it is used
CA	Up to 800 kV; paper-oil insulation with top core (live tank); accuracy of up to 0.1 % stable over the life of the unit; primary currents from 1 to 5,000 A; short-circuit current up to 120 kA for 1 s	High and extra-high voltage substations, metering points, protection
CX	Up to 72.5 kV; dry insulation; accuracy of up to 0.1 %; primaries from 1 to 2,400 A; short circuit up to 50 kA for 1 s; compact design	Subtransmission networks and plants where size and oil matter
LB and CG	Own datasheets in the same catalog	Identified by the nameplate; specifications are taken from their datasheet

Arteche states that its current transformers can feed protection relays. According to the manufacturer, they are suitable for metering points because of their high accuracy. They also have good frequency response, which allows power quality monitoring and harmonic measurement. They are also applied in AC filters of converter stations in HVDC (high-voltage direct current transmission) projects. The manufacturer publishes user manuals for current, inductive and combined transformers in several languages, including Spanish, English, Portuguese, French, German and Chinese, and environmental product declarations (EPD) for the current transformers.

What IEC 61869-2 sets and why it matters when reading a datasheet

IEC 61869-2:2012 (edition 1.0, published on September 18, 2012 by technical committee TC 38) is the standard for additional requirements for inductive current transformers, applicable to newly manufactured units with rated frequencies from 15 to 100 Hz. It is read together with IEC 61869-1 and replaces IEC 60044-1 and IEC 60044-6. The IEC text states that the edition adds technical innovations for transient performance, that is, the requirements of the former IEC 60044-6 for transformers that must reproduce the fault current with a DC component without saturating.

Practical consequences:

An old datasheet refers to IEC 60044-1. A unit manufactured under the previous standard can carry classes and definitions that read the same, but whose normative text is no longer the current one. When comparing a replacement with the unit in service, look at which standard each nameplate cites.
Transient protection classes. The TPX, TPY and TPZ classes do not replace the P classes: they answer different needs. TP classes exist for schemes that must operate during the DC component of the fault. They differ in how much remanent flux they admit and in whether the core has an air gap. We give no values here because they depend on the class and the applicable standard; they must be read from the nameplate and the test report.
Separate cores. In these units the metering and protection windings are on independent cores. The secondary connection to the relay or the meter must match the core, the ratio and the terminal shown on the nameplate; a connection to the wrong terminal is a common source of ratio errors.

Digitalization of measurement

Arteche also offers alternatives to inductive transformers for digital substations:

Standalone IEC 61850 merging units: according to Arteche, they convert the analog signals of conventional CTs and VTs into IEC 61850 sampled values, and there are models for the yard and for the control room. They allow a process bus to be implemented without changing the existing instrument transformer. More in merging unit and IEC 61850 sampled values.
Optical current transformers (SDO-OCT): they work by the Faraday effect, which changes the polarization angle of light as it passes through a magnetic field. The manufacturer highlights their accuracy range, the absence of explosive failure risk, that they use no SF6 and that they are passive: the only active element of the system is the IEC 61850 merging unit.
Capacitor voltage transformers and coupling capacitors: capacitor transformers reduce the line voltage for relays and meters; coupling capacitors are used only to couple high-frequency signals (power line carrier) and are equivalent to the capacitive part of a capacitor voltage transformer. Arteche also notes harmonic measurement together with its power quality sensor.

Acceptance and maintenance tests: what they cover

Without going into procedure, an acceptance and maintenance test plan for a high-voltage current transformer usually covers these tests: ratio and polarity on each core; excitation curve and knee point of the protection cores; secondary winding resistance; insulation resistance; and power factor and capacitance of the unit’s insulation. On oil-filled units the oil condition is added. On current transformers with paper-oil insulation, the power factor should be compared with earlier campaigns on the same unit and not only with a single value (power factor and tan delta).

Frequently asked technical questions

Datasheets for Arteche current transformers: Arteche publishes datasheets by series; the nameplate and the factory report hold the data of the installed unit. When requesting the datasheet, give the series or model (CA, KA, UTD).
What is tested: ratio and polarity, excitation and knee point, winding resistance, insulation and tan delta; on combined units, both parts. See turns ratio test.
Open current secondary: it is dangerous; unused cores are short-circuited and grounded.

How we help

We do not sell instrument transformers. At Tiza Group we test current, voltage and combined transformers of medium, high and extra-high voltage, verify their connections to relays and meters and support commissioning, in substations and in industry. Field work is done in Colombia, or elsewhere on request. See current and voltage transformer testing within testing and commissioning. Write to us through contact.

References

IEC 61869-2, current transformers; IEC 61869-3, inductive voltage transformers; IEC 61869-4, combined transformers; IEC 61869-5, capacitor voltage transformers.
Arteche, datasheets CA Series (HV current transformers), KA Series (HV combined transformers up to 245 kV) and combined transformers; E.ON approval announcement (CA-123 and UTD-123).
Industry Canada, approvals AE-2150 (KA-72 and KA-245).

Frequently asked questions

What is the Arteche CA current transformer?

It is Arteche's series of high-voltage current transformers, of the top-core type, with paper-and-oil insulation. Arteche publishes it up to 800 kV, with primary currents from 1 to 5,000 A, accuracy up to class 0.1 and a short-circuit current of up to 120 kA for 1 s.

What is an Arteche KA combined transformer?

It is a unit that combines a current transformer and an inductive voltage transformer in one body. Arteche publishes the KA series up to 245 kV (for example, KA-72 and KA-245). It saves space and structures in the yard, and is common at metering points and revenue metering.

Where do I find the Arteche instrument transformer catalog?

On Arteche's website, which publishes datasheets by series (CA, KA, voltage transformers and capacitor transformers). To test an installed unit, the data that count are those on the nameplate and in the factory test report: ratios, cores, classes and burdens.