Electrical system design of 614m composite earth p

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Research on the electrical system design of 6.14m diameter composite earth pressure balance shield

Abstract: combined with engineering practice, the electrical system of composite shield is studied, and the characteristics of the system are analyzed from the aspects of power supply and distribution, shield control, detection instruments, data acquisition and so on

Keywords: electrical monitoring characteristics of composite shield

abstract: incorporated engineering practices, this paper studies electrical system from analyses of system characteristics of power supply and distribution, shield control, testing instrumentation, data acquisition on composite shield epbm

Keywords:Compound Shield, shield, electrical monitoring features.

1 overview

φ The 6.14m composite earth pressure balance shield (hereinafter referred to as composite shield) is newly developed by tunnel Co., Ltd. for the construction of Metro Line 2 by Guangzhou Metro Corporation. The shield needs to cross soft soil, hard soil (rock soil), composite soil and other soil layers, and cross the Pearl River. The tunneling distance is about 1.7km. The imported slurry balance shield originally used for the construction of line 1 can no longer meet the construction needs; The other imported EPB shield was damaged at the end of the construction of line 1. In order to adapt to the construction of line 2, the slurry balance shield must be completely transformed

the composite shield should be suitable for both the construction conditions of soft soil and the excavation conditions of hard soil and composite soil (soft and hard soil mixed). It adopts the intersecting cutter head of the combination of hob and cutter arranged in full face cutting to excavate the rock and soil. When the rock and soil of the working face are stable, it can excavate under the unbalanced state of soil pressure; When encountering soft soil and complex strata, tunneling will be carried out under the state of earth pressure balance to ensure the safety and quality of the project. When the composite shield is constructed in soft soil, its balance mechanism is consistent with the general earth pressure balance shield, which keeps the earth pressure of the sealed chamber filled with cutting soil at the set value to obtain the stability of the shield excavation surface; The significant difference is that the composite shield has greater cutting capacity and more complex control functions, so the power of the cutterhead should be greatly increased and has a variety of control modes. However, the tunneling mechanism of slurry balance shield is completely different from that of earth pressure balance shield. It relies on slurry dynamic balance to achieve the stability of the excavation surface, and uses slurry transportation and slurry treatment to discharge soil; Its structure and equipment configuration are also completely different. Taking the equipment configuration of the shield as an example, the earth pressure balance shield needs to add screw machines, belt conveyors and other auxiliary equipment, so it is difficult to transform the slurry balance shield into an earth pressure balance shield, and it is even more difficult to transform into a composite earth pressure balance shield

2 overview of the original slurry balance shield

according to the field survey in Guangzhou, the shield has been disassembled into cutterhead, cutting ring, support ring, assembler, rounding device and other parts (loose parts) and stacked in the open warehouse. The shield machine has 7 trolleys in total. The control room is set on trolley1, the power equipment is distributed on trolley2 ~ 6, and the low-voltage distribution cabinet is installed on trolley7. The main electrical equipment of the shield body includes: console, high-voltage cabinet, low-voltage cabinet, capacitor cabinet and instrument cabinet; 14 motors; 14 sensors (sets); 1 set of remote control device; More than 80 solenoid valves; 1 set of PLC (host a3ncpu, 30 input/output modules); There are several button boxes and limit positions on site (many are lost and damaged)

the independent slurry transportation system is designed and manufactured by Japan's Taipingyang company. In the shield, there are switching valve, ev valve, sludge pump, control cabinet (box), sludge pump flowmeter and densimeter. PLC is a self-contained system, with one master station and four slave stations. The master station and slave station communicate by me signal transmitter

3 difficulties of research

(1) the development of composite shield needs to start from the study of shield working mechanism, and then carry out the design and research of electrical system after in-depth study of control mode and construction management mode

(2) the old slurry shield is reformed, and the design lacks complete technical data of the original shield. In the absence of the required system schematic diagram, sensors, instruments, PLC and other technical data, it is necessary to thoroughly digest and study the original imported electrical equipment, master the basic technical performance, allow the addition of pigments and additives and parameters, and provide the necessary data for the reform design

(3) due to the limitation of the technical parameters of the original equipment (components), it is necessary to coordinate the matching of various technical parameters and components of the old and new equipment, so that the system can operate reliably and reasonably

(4) according to the overall control requirements of the shield and the current construction operation habits, and following the principles of safety, reliability and practicality, an electrical monitoring system with Chinese characteristics is designed

4 key points of design and research

composite earth pressure balance shield is still blank in China. It is also necessary to carry out transformation and restructuring design for the imported old slurry shield, which requires more and more complex research contents. The main points of design and research are:

4.1 power supply and distribution

(1) due to the use of 10kv High-voltage direct power supply, it is necessary to solve the problem of whether the original 6kV high-voltage equipment can continue to be used

(2) the power configuration of the composite shield is twice that of the original shield, and the capacity difference of a single shield is large. How to use the original low-voltage power distribution equipment to make the control and protection functions of each power circuit better than the original shield

(3) the original power supply and distribution configuration is relatively simple. How to improve the safety and reliability of the shield power supply and distribution system

(4) unreasonable layout of original equipment. With the use of old trolleys (No.1 ~ No.7) and the increase of equipment, how to reasonably arrange the equipment can not only save cables, but also facilitate installation and maintenance

(5) the original PLC, instrument, solenoid valve, lighting and control share one power supply (1 set of 7.5kVA, 400v/100v transformer). How to improve reliability and solve the contradiction of capacity increase

4.2 technological process of shield machine

the technological process of composite shield machine is more complex than that of soft soil shield. The operation of composite shield machine is divided into three different modes: hard soil, soft soil and composite soil, and different modes have different technological processes; Moreover, each equipment also has special process flow, such as cutter head lubrication pump, double liquid grouting, etc. According to the functions and requirements of shield machine, explore and study the general process flow of composite shield and the process flow of corresponding equipment

4.3 shield control

(1) the configuration of the original shield control system cannot meet the control requirements of the composite shield, and a new control system must be built to meet the construction requirements

(2) study three different modes and the control of cutter head, hinge, propulsion, lubricating grease, rounding device, etc

(3) improve the anti-interference ability of PLC hardware and the reliability of software

(4) starting from the system, study the power signal transmission relationship between power supply and distribution, sensors, instruments, controllers and computers, and systematically coordinate the relationship between software and hardware

(5) the wiring of the remote control device of the assembly machine is complex and there is no data, so its function must be restored and continue to be used

4.4 detection instruments

(1) the detection objects of the composite shield are far more than the original shield, so reliable and practical detection elements and methods must be used to meet the demand of increasing detection content

(2) make full use of the original sensors, displays and other detection instruments to form a complete detection and display system

4.5 computer data acquisition

the original data acquisition system no longer exists. From the electrical circuit analysis, the system can not directly communicate with the PLC system. The interface of the analog signal provided by the original instrument cabinet is far from meeting the needs of the composite shield monitoring system. It is necessary to rebuild a computer data acquisition system to meet the requirements of real-time data acquisition and historical data management of composite shield, and provide a good man-machine interface and data acquisition

5 electrical system characteristics of composite shield

due to the low voltage withstand level of the coil of the original power transformer, it cannot be reformed, and the original power transformer cabinet is too long to be used. Therefore, we can only use some components such as low-voltage electrical appliances, PLC, detection instruments, as well as the cabinet of console and instrument cabinet to redesign the shield system according to the control requirements of composite shield

5.1 power supply and distribution system

the composite shield adopts 10kv High-voltage power supply, with a total capacity of about 1360kw. Two 10/0.4kv power transformers (1000KVA and 800kVA) are used for power distribution respectively. See Figure 1 for its power supply and distribution system

5.1.1 high voltage power supply

the ground supplies power to the shield high voltage switchgear through UG mining rubber sheathed cable. The high-voltage switchgear is composed of one high-voltage incoming cabinet and two transformer protection cabinets. The high-voltage switchgear is equipped with load switches, and the transformer protection cabinet is equipped with high-voltage fuses and load switches. Since the switch cabinet of Alstom is indoor equipment, another high-voltage cabinet is designed to improve the protection level. ABB's dry-type power transformer is selected, and the transformer cabinet is designed. The cabinet is equipped with a temperature controller and an exhaust device, which can monitor the temperature of each phase of the power transformer and control the exhaust

5.1.2 low voltage distribution

the power transformer supplies power to two low-voltage distribution cabinets (1c and 2C cabinets) respectively, forming two independent distribution systems. Each low-voltage distribution cabinet is equipped with a total leakage circuit breaker, which has short-circuit, overload, leakage and other protection. The problem of 1C cabinet for plastic landfill in the shield and No. 1 ~ 4 is now mainly the volume problem. The power supply of all equipment on No. trolley is rated at 1450a; 2C cabinet distributes power to all equipment on No. 5 ~ No. 7 trolleys, and the rated operating current is 1150a. See Table 1 for the configuration of power equipment. The equipment shown in * in the table is controlled by PLC, and is additionally provided with phase failure, phase reversal, overcurrent, emergency stop and other protections

each power circuit is equipped with short-circuit, overvoltage, overload and leakage protection

control (including solenoid valve) and PLC (including instrument) are powered by their respective transformers

set low-voltage power compensation equipment, configure two power factor compensation cabinets, equipped with 230kvar and 190kvar capacitors respectively, and use PLC to control automatic switching of compensation capacitors to improve power factors

5.1.3 shield lighting

the original lighting adopts 100V power supply, and each trolley has only one set of lamps, which cannot meet the illumination required for shield construction. Now, a lighting cabinet is set separately, and the voltage of 400V is reduced to 220V by three 5KVA transformers as the lighting power supply. The shield is only equipped with fixed lighting, and adopts waterproof lamps, which are divided into 12 branches, and each branch is equipped with two-level leakage protection; The shield and each trolley are equipped with three sets of fluorescent lamps, including one set of emergency fluorescent lamps; The assembly area and the head and tail of the trolley shall be equipped with projection lamps to enhance the lighting of the shield working face

5.2 monitoring system

the composite shield monitoring system is composed of PLC control system and computer data acquisition system. The PLC control system is equipped with 1 master station and 3 slave stations. The PLC master station and computer (printer) are set in the shield control room. No.1 and No.2 slave stations are respectively set in two low-voltage distribution cabinets, and No.3 slave station is set in the shield (cabinet E). See Figure 2 for the block diagram of its monitoring system. The status signals (control signals) and construction parameter signals of all shield equipment are connected to the corresponding PLC nearby

5.2.1 hardware configuration

plc adopts a series of modules from Mitsubishi Corporation of Japan. The master station is A3A series and the slave station is a1s series. The PLC of the original muddy water system is basically used, the me signal transmitter is cancelled, and the melsecnet/b communication mode is adopted. The communication medium is coaxial cable, and several communication modules are added accordingly

select one amb-562tt industrial control computer (with touch screen) and one epsonlq-300k printer from Weida company to form a data acquisition system

5.2.2 operation and control

using the original console, the operation requirements of the new system can be met through comprehensive restructuring in the cabinet,

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