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IEEE 1627-2019 pdf free download

IEEE 1627-2019 pdf free download.IEEE Standard for Transient Overvoltage Protection of DC Electrification Systems by Application of DC Surge Arresters.
5. Surge environment—DC transit electrification system
Using an OCS as an example, it is evident from dc electrification systems that there are two paths for the surges to impact substation equipment: one from the OCS side and the other from the incoming ac primary power supply system. The expected upper limit of the surge without the dc surge arrester that could propagate through the OCS will be equal to the dry fiashover value of the OCS, which is typically 35 kV peak for 750-V dc systems (Paul, 2004 [131 NJ). Incoming ac primary voltage to TPSSs is generally medium-voltage (MV) and design practice is to apply properly rated ac surge arresters on the primary side of the rectifier transiornwr. This will reduce the surge voltage magnitude on the secondary side of the rectifier transformer, and then application of capacitors in parallel with diodes leaves a remote possibility of lightning surge getting into the dc switchgear.
The incoming primary surge will see the doubling effect at the rectifier transformer due to the change in surge impedance. The intensity of the incoming surge will be related to distribution system parameters and the magnitude of the incoming surge and system impedance parameters. Internal switching surges and surges at the OCS will be related to any of the system operational causes listed in 4.1.2.
Due to the proximity of the OCS positive wire, and the running rails or negative wire in case of an electric trolley bus (ETI3) systems. there are equal chances that the lightning may strike both positive and negative wires simultaneously. Any surge voltage striking the OCS wire is free to propagate toward the dc switchgear, as well as to the vehicle via the current collector. The associated surge current will divide according to the surge impedance paths and will experience some attenuation beftre reaching the equipment if there are no surge arresters between the strike location and equipment.
A discussion of surge environment is provided here for the OCS: however, similar discussion applies to other dc transit electrification systems.
For dc applications, the same nonlinear resistors that are used in ac surge arrester assemblies are used in the dc arrester housing but tested differently. The basic requirements of a dc surge arrester include the following:
a) At highest working voltage, the device shall be essentially non-conducting with a minimal leakage current. IEEE 1627-2019 pdf free download.

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