Testing gloves against high voltages

Tests can be carried out on gloves to assess protection against high voltages.

When working on electric equipment, the risk of electric shock should ideally be removed by switching the equipment off and isolating it from the electrical supply. However, in many situations this is not possible and work must be carried out on live equipment. On these occasions, protective measures include the use of a range of insulating items such as insulated tools to handle live wires and protective blankets to cover live equipment. Workers must also be equipped with suitable personal protective equipment (PPE), such as insulating gloves, which have been tested and approved as providing an acceptable level of protection against contact with a high voltage.

Historically, insulating gloves have been tested against ‘alternating current’ (AC), since most power distribution networks use this form of electricity supply. However, in more recent times ‘direct current’ systems (DC) have become much more common, with the rise in renewable energy sources such as solar panels, and to address the needs of electric vehicles. Although an electric vehicle can be charged from an AC source and may even have an AC motor, the battery provides direct current. Systems for fast charging of the battery also use direct current. Therefore, there is a growing need to be able to prove the performance of insulating gloves against DC sources.

Overview of tests

The European standard covering such gloves is EN 60903:2003 – ‘Live working. Gloves of insulating material’. A more recent version of the standard has been published as IEC 60903:2014. Both versions include a range of tests, some of which are optional and only carried out if a special property is to be claimed. The mandatory test assessments include checks on dimensions, finish, marking and packaging, plus evaluations of basic mechanical performance, dielectric properties, ageing treatments and thermal tests.

The IEC version is generally technically identical to the EN version. However, slight differences between the two exist – for example, in the conditioning process for the basic proof and withstand dielectric tests.

Both standards include requirements for composite gloves which have enhanced mechanical strength, including resistance to abrasion and tearing. Resistance to cuts is also included, and in both versions the blade-cut test identical to that used in EN 388 is specified. The IEC version, however, permits the use of the ISO 13997 straight blade-cut test.

The basic mechanical performance tests cover tensile strength and elongation at break, tension set and puncture resistance. In the dielectric tests, gloves are tested at the specific proof and must withstand voltages for the class claimed or marked on the glove (see table 1). The thermal requirements consist of a flame retardancy test on the glove fingers and exposure to a -25°C environment, following which the gloves are checked for cracks and then subjected to the proof test at the specified voltage. For gloves with claimed special properties, the associated marking codes are listed in table 2. These special properties are tested by applying the specified exposure conditions, following which the gloves are subjected to the proof test. For acid and oil resistance, tests for tensile strength and elongation at break are also carried out on the exposed gloves.

Table 1: Dielectric tests
Class	Maximum use voltage (voltage rating)	Colour code*	AC proof test voltage (kV rms)	AC withstand test voltage (kV rms)	DC proof test voltage (kV)
00	500V ac/750V dc	Beige	2.5	5	10
0	1,000V ac/1,500V dc	Red	5	10	20
1	7,500V ac/11,250V dc	White	10	20	40
2	17,000V ac/25,500V dc	Yellow	20	30	50
3	26,500V ac/39,750V dc	Green	30	40	60
4	36,000V ac/54,000V dc	Orange	40	50	70
*Optional colour code for marking symbols

Table 2: Optional tests on gloves with special properties
Special property	Marking code
Acid resistance	A
Oil resistance	H
Ozone resistance	Z
Acid, oil and ozone resistance	R
Extreme low temperature	C
Increased mechanical properties (abrasion blade cut, tear)	Mechanical pictogram

SATRA HV test equipment

Figure 1 shows the high voltage apparatus used in SATRA’s laboratories for EN 60903:2003 and IEC 60903:2014 dielectric testing.

Before the basic dielectric testing, gloves are fully immersed in water for 16 hours. In the EN 60903:2003 test, the gloves are then carefully dried by hand. The prepared gloves are filled with water and immersed in a tank of water so that the distance between the cuff and the water level inside and outside is as detailed for the specific class of glove. In IEC 60903:2014, following the 16-hour water immersion, the gloves are placed in an air oven at 70 ±2°C for 0.2 ±0.1 h before filling with water and carrying out the dielectric tests.

The dielectric testing on gloves intended to be used on AC installations includes an initial three-minute proof test at the specified voltage (see table 1). The leakage current is measured after three minutes then the voltage is reduced back to zero. Then, a withstand test is carried out at a higher voltage than the proof test (also see table 1) to ensure that no electrical puncture occurs in the sample. It should be noted that proof tests on gloves subjected to exposure to ageing, acid, oil, low and extremely low temperature and ozone are conducted without the 16-hour immersion test.

For gloves intended to be used on DC installations, a proof test only is carried out and for a duration of one minute.

Further information on SATRA's PPE certification and testing services is available at www.satra.com/ppe

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