Anti interference measures for remote signaling of

Anti interference measures for remote signaling of small current grounding line selection device

Abstract: these materials under the jurisdiction of our bureau are usually very sensitive to humidity and temperature. Through the "four remote" transformation, 110kV substation realizes unattended. When a single-phase grounding fault occurs in the 10kV line, the mln-98 small current grounding line selection device in the substation judges the grounding line, and its remote signaling interface sends the line selection signal to the dispatching end through RTU. The dispatcher informs the power supply company to patrol the line and eliminate hidden dangers. In operation, when the 10kV line is single-phase grounded, the dispatcher does not receive the line selection signal from time to time. After inspection, it was caused by the interference of remote signaling public power supply to small current grounding line selection device

key words: small current grounding line selection device remote signaling anti-interference 110kV substation under the jurisdiction of our bureau has realized unattended through "four remote" transformation. When a single-phase grounding fault occurs in the 10kV line, the mln-98 small current grounding line selection device in the substation judges the grounding line, and its remote signaling interface sends the line selection signal to the dispatching end through the RTU. The dispatcher informs the power supply company to patrol the line, and the hidden dangers should be eliminated evenly. In operation, when the 10kV line single Jinan experimental machine factory steel wire hydraulic universal experimental machine project detection method is grounded, the dispatcher does not receive the line selection signal from time to time. After inspection, it was caused by the interference of remote signaling public power supply to small current grounding line selection device. 1. Principle of remote signaling interface mln-98 principle of remote signaling interface of small current grounding line selection device is shown in Figure 1 (for simple expression, only one channel is drawn). The calculation and processing chip U1 judges the grounding fault line, selects the corresponding outlet channel through the chip selection U3, and the non gate U7 drives the remote signaling outlet relay jrc1 to act. The contact is connected, and the line selection signal is output to R47 year old Li Moumou, who claims to have family difficulties Tu. The line selection signal is maintained for 200ms, and the computer master station displays an alarm at the dispatching end after confirming the signal. When the ground fault disappears or the reset key SW1 is pressed for manual reset, the "res" position changes from high potential to low potential, U1, U3 and other elements are reset, the driving signal of the remote signaling outlet relay disappears, the contact is opened, and the grounding line selection signal output to the RTU disappears. 2. In the simulated grounding test of remote signaling public power interference, the line selection device LCD display and printed information show that the line selection is correct. Connect the remote signaling public power supply, and the relay contact at the remote signaling outlet of the device is instantly connected, but it cannot be maintained, and the dispatcher cannot receive the grounding line selection signal; Unlock the remote signaling public power supply and close the contact. The remote communication common power supply of Siemens SINAUT 8fw RTU used in the substation is DC 50V, while the VCC power supply in mln-98 small current grounding line selection device is DC 5V. The capacity of the original anti-interference capacitor C3 is insufficient. In the high-speed electronic circuit, the interference generated by the closing of the contact of the remote signaling outlet relay will affect the potential of VCC, form a low potential to reset U1 and U3 chips, the driving signal of the remote signaling outlet relay disappears, the contact is opened, the line selection signal output to the RTU cannot be maintained, the computer master station cannot confirm, and the dispatcher cannot receive the fault information. 3 anti interference measures to enhance the anti-interference ability, it must be connected in parallel at C3 2.2 μ Tantalum capacitor C '(electrolytic capacitor is not available, and its inductance is too large). C 'can be welded between pins 10 and 6 of the remote signaling interface board JP1 (16pin) of mln-98 device, as shown in Figure 2. The capacitance increases, which can effectively filter out interference, stabilize the VCC potential, and maintain the line selection signal. After taking countermeasures, the dispatcher can receive the grounding line selection signal during the simulation test and the single-phase grounding fault of the line, and the problem is solved. In order to prevent interference, the manufacturer is recommended to add a level of photoelectric isolation at the remote signaling outlet of the grounding line selection device, as shown in Figure 3