Views: 2 Author: Site Editor Publish Time: 2021-10-12 Origin: Site
The Ovation system's requirements for grounding methods are summarized from five aspects: cabinet insulation, busbars, grounding points, grounding system descriptions, and grounding general rules.
1. Cabinet insulation requirements
· The cabinet needs to be insulated with channel steel, and the insulation resistance should not be less than 5MΩ.
· Insulation rubber should be laid between the cabinet and the channel steel, and the thickness of the rubber should not be less than 8mm.
· The cabinet fixing bolts need to be covered with insulating sleeves to avoid the connection between the cabinet and the channel steel through the fixing bolts.
2. Confluence Bronze Requirements
· A grounding busbar must be provided, and all Ovation equipment grounds are connected to the busbar
· Non-Ovation equipment cannot be connected to this busbar.
· The busbar is connected to the grounding network of the whole plant through the grounding cable, and no transfer is allowed in the middle.
· The size of the busbar should not be less than 400 x 40 x 8 mm (length x width x thickness).
· In general, there will be equipment of other systems in the operator station besides the host computer of the Ovation system. Therefore, the grounding of the operator station is not recommended to be connected to the grounding copper bar of the Ovation system. It is recommended to connect directly to the grounding device near the centralized control room. Can
3. Ovation grounding point requirements
· The grounding of strong electric equipment is not allowed near the grounding point of the Ovation system
· There is no grounding of lightning protection equipment within 15 meters of the grounding point of the Ovation system
· There is no grounding of high and low voltage electrical equipment above 30KW within 8 meters of the grounding point of the Ovation system
· When the above conditions cannot be met on site, the lightning protection ground should be connected to the public grounding grid through a lightning arrester/shock wave suppressor.
· Do not overlap the electric welding ground with the common ground electrode and its grounding grid, and the distance between the two should be more than 10 meters.
· The ground cable from Ovation equipment to the ground busbar and the ground cable from the busbar to the grounding grid of the whole plant should be as short as possible.
4. DCS grounding system description
· The cable from Ovation equipment to the grounding busbar should not be less than 4 AWG (cross-sectional area: 21.1mm²).
· The cable from the grounding busbar to the grounding grid of the whole plant must be no less than 0 AWG (cross-sectional area: 53.5mm²).
· The grounding resistance should not be greater than 1 ohm.
· The grounding cable from the Ovation cabinet to the grounding busbar should be connected to the dedicated grounding post (CG) on the mounting plate in the cabinet.
· The Ovation system allows multiple cabinets to be grouped together and connected to the grounding busbar.
· The number of cabinets in each group cannot exceed 5
· The distance from any cabinet in a group to the grounding central cabinet (the grounding cable to the busbar is connected from the cabinet) cannot be greater than 10m.
· Only the PG-CG short-circuit copper plate is allowed to be installed in the grounding center cabinet in a group. If the other cabinets in the same group still have the short-circuit copper plate, they need to be removed.
· The grounding cables between the cabinets in a group are provided by Emerson.
5. DCS system grounding general rules
· For the grounding of I/O points, the general principle is to ground on the DCS side
· When the signal source is floating, the cable shielding layer is grounded on the DCS side.
· When the signal source is grounded, the cable shielding layer is grounded on the signal source side.
· When the shielded cable is divided or merged through the junction box, the shielding layers of the two ends of the cable should be connected in the junction box.
· The main screen of the multi-core shielded cable is connected to the grounding copper bar in the · · · Ovation cabinet. The split screen must be connected to the SH or E terminal corresponding to the card. The split screen cannot be connected to the grounding copper bar in the Ovation cabinet.