FIELD OF THE INVENTION
The invention generally relates to a system for monitoring Heaters status, and Ash level status of Electrostatic precipitator used for air pollution control. Electrostatic precipitators are used in Thermal power stations / Industrial applications to collect fly ash particles from flue gas leaving boiler furnace to avoid air pollution. More particularly, the invention relates to a system and a method for monitoring the ON/OFF status of Hopper heater, shaft and support insulator heating elements and Ash level status in hoppers of Electrostatic precipitator.
BACKGROUND OF THE INVENTION
Electrostatic precipitation is one of the most effective processes to control air pollution generated by industrial emissions. This technique, which has proven to be highly effective in controlling air pollution, is used for removal of undesirable matter from a gas stream by electrostatic precipitation. Electrostatic precipitator (hereafter referred as ESP) is an air pollution control device designed to electrically charge and collect particulates generated from industrial processes, such as those occurring in power plants, cement plants, pulp and paper mills and utilities etc. The electrically charged particles are attracted towards electrode plates, viz., and discharge electrode and collection plate.
Hoppers in Electrostatic precipitators are used to temporarily store the fly ash particles collected from flue gases by collection mechanism of ESP, during its flow from furnace to chimney. Support insulators are used for hanging High voltage electrodes of ESP and Shaft insulators are used in rapping mechanism for removing collected ash particles from electrodes. Once ash level in hopper exceeds a particular level, ash is evacuated by ash handling system.

An ESP installation consists of a plurality of fields, each field having one or two number of Hoppers for each field for storing the collect fly ash particles. For a typical larger ESP, there will have around 8 pass's and each pass will have around 10 fields and 10 to 20 numbers of hoppers depending on the ESP design based on inlet dust burden ash evacuation system. In ESP the collected fly ash is removed from the collecting electrodes by hammering action, which is operated by rapping motors. During rapping time the ash particles collected in collecting electrodes will leave the collecting electrode and it will deposit in area called Hopper of ESP. The collected fly ash has to be kept above certain temperature to maintain its fluidity. Hence hopper is heated up to certain temperature by using electric heating element; its operation is controlled by thermostat. When hopper temperature exceeds the set temperature thermostat will break the electrical circuit, and avoid excess heating and save electrical power consumption. Flue gas temperature inside ESP is around 120 degree centigrade and above, Due to temperature gradient, the chance of forming crakes in shaft and support insulators is more. In order to avoid failure its temperature also maintained at 120 degrees by using electric heating elements. The ash collected in hopper is removed periodically by using pneumatic arrangement for proper functioning of ESP. Ash level low indicators are provided to ensure whether hopper is fully evacuated, and to stop evacuation of Ash. Hence, in order to monitor the Heaters status and Ash level status, it is necessary to introduce a monitoring mechanism.
In the prior art, monitoring of heaters and Ash level are achieved through independent controller. There will one controller per pass of the ESP. For increasing its availability, additional redundant or Standby Controllers are to be provided. However, for such cases, the total number of monitoring Controller will be doubled.

In the prior art, there is no monitoring controller configuration through which monitoring of the entire PASS can be done by a single EC-HVR Controller. Also, there is no method to increase the availability of monitoring Controller of the entire ESP using a single standby monitoring Controller avoiding doubling of monitoring Controller nos.
OBJECTS OF THE INVENTION
The object of the invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash level status of electrostatic precipitators (ESP) having a group of EC-HVR controllers in one pass, in which one of the EC-HVR controller acting as Master for monitoring operation.
Another object of the invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash level status of electrostatic precipitators (ESP), in which EC -HVR controller have intelligence to switch over from the role of Master Controller to slave controller and vice-version in case of failure of Master controller to ensure sustained monitoring operation of all the fields of a Pass.
A still another object of the invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash level status of electrostatic precipitators, in which each of the EC-HVR controller have ability to act as master controller at one point of time when others acting as slave controllers.
Yet another object of the invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash

level status of electrostatic precipitators, which further performs high voltage rectifier transformer controlling operation.
A further object of the invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash level status of electrostatic precipitators, in which each controllers has a device to display the heater status and ash level.
A still further object of this invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash level status of electrostatic precipitators, which is configurable as per the power plant requirement such as number of fields to suit same hardware for all functional areas.
Yet further object of the invention is to propose a system for monitoring ON/OFF status of Hopper heater, heating elements of shaft and support insulator and ash level status of electrostatic precipitators, which is provided with advanced communication means such as RS485, CAN for free transmission of the data to ESP single point controlling system and plant Distributed control system (DCS).
SUMMARY OF THE INVENTION
The invention adopts a Pass master control logic module to interface a group EC-HVR controllers of a pass connected over a common RS 485 communication channel, to facilitate status monitoring operation of the pass in addition to HVR transformer controlling. The input cards are used for reading Heater ON/OFF status feedback and Ash level status. All the controllers in the pass and cards are connected by a common RS485 communication channel functioning on MODBUS protocol.

The invented system has in-built intelligence to handle the communication over the bus connecting the master and slave controllers. The Pass master logic module based controllers, receive and process the data over the two wire RS485 communication channel over MODBUS protocol, and assign self as Master/ Slave and also update the status of heaters and ash level of the respective field in addition to functioning as high voltage transformer controller.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a block diagram of a Pass Master Logic module based monitoring system using high voltage rectifier transformer.
Figure 2 - shows the internal block diagram of an Electronic controller of the monitoring system.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Figure 1 shows a hardware block diagram of the control system having a group of electronic controllers in one pass of ESP, in which one of the controllers can acts as a Master at a particular time based on pass master logic available in each of the controllers for status monitoring. Pass master Logic is a software logic to distinguish/assign one of the controller as Master and others as slaves in a group, which is formed by using a common communication link.
In Figure 1, blocks (1) to (7) form a group of electronic controllers assigned for one pass of the ESP (8) having Pass master logic module to assign one as the Master in the group and others as the slaves. Block (9) is a RS 485 communication channel, which connects all the controllers in the pass (8) and an input card. The input cards are used for collecting status of heater and Ash level inputs from the ESP fields of a pass. The HVR controllers the ESP, are located in

the electronic controller panel room control a high voltage rectifier transformer. The input cards are located at the bottom of ESP structure adjacent to the hoppers.
The hardware block diagram of an Electronic controller is shown in Figure (2). In Figure (2), block (12) is the power supply unit for the controller. In Figure (2) block (13) is the RS 485 communication interface connecting all the controllers, input card and ESP single point controlling system. In Figure (2), block (14) is the central processor (Micro controller) which executes the software execution. It has inbuilt memory to store the program. In Figure (2), block (15) is a liquid crystal display of the status and other parameters.
Each of the EC-HVR controllers has separate setting for its address, Pass name as well as field number. Controller address is unique and it is used for establishing communication with remote access point. The Pass master logic module works based on the field number assigned to the controllers forming the pass. Once the controllers in a pass are energized, the controller having the highest field number, will send command through the common communication channel (9) which links all the controllers, input cards and wait for a reply. If the reply from the input card is received, that controller will become Pass master and take over the function of monitoring of the heater status and ash level status of the pass. Other controllers assume themselves to act as slave as long as they receive reply from the input cards.
The Pass master control logic having in-built intelligence to assign only one controller as Pass Master at a time in a pass. The Pass master logic works as follows; suppose if there are N fields in a pass then there will be N numbers of controllers having field number setting 1 to N. The time delay assigned for each controller for assigning self as master of the system is calculated by subtracting N (No of Fields in a Pass) with field number assigned to that particular controller. Obviously it will be zero for the controller having last field number, i.e., N. It will

become 1, 2 3, 4, 5, 6, 7, 8 time units for successive controllers. Hence once the pass is energized, the controller having highest field setting will command first in the common RS 485 communication bus. If it fails the next controller having lowest time delay will command and assumes as master and starts monitoring operation of a pass in addition to HVR transformer control and all other as slaves take care of charging of HVR transformer of field to which it is connected. The slave controllers continuously monitor the healthiness of the Master controller based on the commands reception from the Pass master controller and reply via input cards over the common RS 485 communication link [9]. If slave controller doesn't receive any command from master controller, it detects the failure of the master controller, and accordingly, the controller having lowest time delay will automatically assume as the Pass master. In Pass master based rapping system having 'N' levels redundancy (Where N is the no of the field) i.e., if any one of pass master fails , next controller having minimum time delay will automatically pick up as the Pass master.
Indication is available in the controller to identify which controller is acting as the pass master at a particular time. In this system, the Heater ON / OFF and Ash level information is transmitted by the input card to the Master Controller as well as other slave controllers over the serial communication link [9] using standard Modbus protocol. Each controller receives the data packet over the RS485 communication link, processes the data and updates its own LCD display available in the controller. Each controller in a Pass can display the status of the Field for which it is assigned. At the same time, the Pass master can display the status of all the heaters and Ash level in the Entire Pass of ESP.

WE CLAIM
1. A system for monitoring ON/OFF status of Hopper heaters, heating elements of shaft and support insulator and ash level status of electrostatic precipitator (ESP), comprising a plurality of fields, generated and maintained by high-voltage rectifier transformers, controlled by EC-HVR controllers (1 to 7), each controller is assigned with a field number; connected via a common communication link (9) along with input cards. The input cards located at the bottom of the ESP adjacent to the hoppers for reading feedback data relating to ON/OFF status of the heater including ash level status, wherein the controllers having Pass-master control logic module have in-built intelligence allows one of the plurality of controllers to act as a master controller at one point of time when the other controllers operate as slave controllers, wherein upon failure of the assigned master controller, the slave controller with highest field number automatically takes over the functioning of the failed master controller, the remaining Controllers operating as slave Controllers, and wherein the high voltage rectifier (HVR) Controllers controlling the rectifier transformer located on the electronic Controllers panel.
2. The system as claimed in claim 1, wherein all the controllers have parameter back up and user settings similar to that of master controller for functioning of the system during the failure off the Master controller.
3. The system as claimed in claim 1, wherein all the controllers perform HVR transformer controlling based on ESP flue gas flow and other parameters, in addition to control and status monitoring of the heater and ash level in the hoppers.

4. The system as claimed in claim 1, wherein the Controllers are microcontroller based intelligent systems.