Grid power control system of oil rig is divided into the all-electric and semi- electric power systems.
All-electric grid power system
The grid power control system of oil rig, composed of 10KV industrial grid incoming lines, supplies power for two 10/0.6KV 3150KVA dry-type epoxy-resin filled transformers through high-voltage switchgear. Outgoing lines of transformers and low-voltage draw-out type switchgear form a 600V power grid that provides working power for the electric drive and control system of drilling rig. The 600V grid is connected with imported dynamic active harmonic suppression devices and TSF dynamic reactive power compensation devices in parallel for harmonic suppression and reactive power compensation of the grid, improving grid quality and ensuring reliable operation of the system. The whole system is designed with two control rooms, namely the high voltage room and low voltage room.
Dynamic active harmonic suppression device
This device is an electronic product designed with digital logic circuit for current detection and injection, which is mainly composed of active filters and connected with the compensated harmonic load or grid for real-time detection of non-linear load current waveform, separation of harmonic signals, and conversion of detected harmonic signals into digital signal for DSP (digital signal processor). Meanwhile, DSP generates a series of PWM signals for controlling IGBT trigger, and current that is the same in amplitude but opposite in direction with/to harmonic current for injection into the grid, so as to filtrate harmonics, dynamically compensate system fluctuations and increase the power factor.
HV switchgear
● Modular structure ● Designed with protective relay and sensor
● Flexible operation ● Complying with requirements for use
● Designed with “five protections” for lock-out.
Dynamic reactive power compensation device
This device adopts the zero-crossing switching technology of thyristor current to realize zero-current cut-in, zero-current cut-off, no- inrush and no-impact rapid tracking of reactive changes in system load, real-time and dynamic response to switching within a time ≤30m for compensation of fundamental reactive power at a factor over 0.9.
GCS LV draw-out type switchgear
GCS switchgear or drawer cabinet, designed with the functions of maintenance and locking of control units, is used for low-voltage power supply, control and protection of the system.
APF+TSF full digital high-capacity electric energy quality management system is composed of voltage-type active filter and L-C reactive filter. It is effective for constraint of harmonics and compensation of reactive power generated during operation of DC or AC electrical control system of oil rig.
Semi-electric grid power system
Drive and power supply modes of original drilling rig: 3-4 diesel generator sets are connected in parallel to drive sludge pump, winch and rotary table, and auxiliary generator or energy-saving generator is provided for power supply for drilling and living areas.
Modification plan for mechanical part:
Three 800KW or 1000KW or 1100KW motors and variable speed fluid coupling (or reduction gearbox) are used for replacement of 3 diesel engines and hydraulic reduction gearbox; drilling and living power is supplied by the 400V transformer in the electrical control room; in case of grid failure, the emergency generator or original emergency system newly added will be put into operation.
Two plans for modification of electrical part
Plan 1: Variable frequency drive
A mobile transformation and distribution system is used for change into 600V voltage, and 600V asynchronous variable-frequency motor + fluid coupling or reduction gearbox for power supply for drilling rig. AC variable-frequency governor drives asynchronous motor, and 600V/380V dry-type transformer supplies power for the 380VMCC/VFD system. Under the circumstance of industrial grid failure, the 380V auxiliary generator set will provide power supply for the MCC/VFD system, and the emergency system will support emergency operation of drilling rig.
Plan 2: Soft-start drive
A mobile transformation and distribution system is arranged for change into 660V voltage, and 660V asynchronous motor + variable speed fluid coupling for power supply for drilling rig. Intelligent electronic soft starter is used for starting up asynchronous motor, and 660V/380V dry-type transformer for power supply of the 380VMCC/VFD system. Under the circumstance of industrial grid failure, the 380V auxiliary generator set will provide power supply for the MCC/VFD system, and the emergency system will support emergency operation of drilling rig.
