ANSI C37.85-2002 pdf download Alternating-Current High-Voltage Power Vacuum Interrupters— Safety Requirements for X-Radiation Limits
The container for the insulating medium shall be of an insulating material having radiation attenuation no greater than that afforded by 9.5mm thick methyl methacrylate. The insulating medium between the interrupter and radiation instrument shall be the minimum required for dielectric purposes.
5.1.3 Test circuit The interrupter shall be connected to a power source of alternating-current voltage with a means for varying the voltage across the open contacts of the interrupter. A sine wave voltage having a crest value not exceeding 1.414 times the rms value shall be applied.
5.1.4 Frequency The frequency of the supply voltage shall be 50 Hz or 60 Hz. During the test, the frequency shall not vary by more than 3 Hz.
5.1.5 Radiation instrument A radio frequency (RF) shielded radiation survey instrument having the following minimum specifications shall be used: Accuracy: Capable of measuring 15 milliroentgens per hour with an accuracy of ± 25 percent with a response time not to exceed 15 seconds Energy Response: 12 kiloelectron volts to 0.5 mega-electronvolts ± 15 percent Sensitive Area: 100 cm 2 , maximum. NOTE—Victoreen Instrument Company Model 440RF was used during the development of this standard.
5.1.6 Location of radiation instrument The sensing element of the radiation instrument shall be positioned in the plane of the separable contacts and pointed at the contacts from a distance of 1 meter from the nearest external surface of the interrupter (see Figure 1). When electrical safety requires the instrument to be located at a distance greater than 1 meter, the instrument reading shall be adjusted by applying the inverse square law as follows: R (1 meter) = R (d) x (d) 2 Where R (d) is the radiation level measured, at the distance d (in meters) from the external surface of the vacuum interrupter.
5.1.7 Precautions If distances normally required for electrical safety are maintained, the exposure to test personnel will generally not exceed established dose limits (see ANSI N43.3-1993). Nevertheless, adequate precautions such as shielding or distance should be used to protect test personnel against possible higher X-radiation occurrences due, for example, to incorrect contact spacing, or to the application of voltages in excess of those specified in 5.2.