WO1999014720A2

WO1999014720A2 - Method and arrangement for supervising power supply equipment

Info

Publication number: WO1999014720A2
Application number: PCT/FI1998/000722
Authority: WO
Inventors: Jari Raussi
Original assignee: Nokia Networks Oy
Priority date: 1997-09-16
Filing date: 1998-09-15
Publication date: 1999-03-25
Also published as: AU9165398A; FI973700A0; WO1999014720A3; FI973700A

Abstract

The invention relates to a method and arrangement for supervising the operating condition of a power supply system comprising parallel rectifier units. Each rectifier unit to be supervised is equipped with a power supply (211, ... 251) so that if the specified feature of the unit is in order, the power supply feeds a constant current (e.g. I1), but when there is a failure, it does not feed the current. The signal currents fed by different units are summed, and the sum current (I) is passed along the conductor pair (205) through the reception circuit (110) of the control unit. The value of the current (I) then indicates the number of rectifier units that are operational. If there are several types of failures that are monitored, an arrangement like this is provided for each type separately. The information given by the current signals is used to give an alarm. By means of the arrangement according to the invention, the type of urgency of the alarm can be determined at once, which is an advantage for maintenance. In addition, the costs of cabling between the rectifier units and the control unit are relatively low.

Description

Method and arrangement for supervising power supply equipment

The invention relates to a method defined in the preamble of Claim 1 and an arrangement defined in the preamble of Claim 3 for controlling the operating condition of power supply equipment comprising several parallel rectifier units.

In order to improve reliability, one large unit is often replaced by small parallel units on the principle N+l . (There is one unit more than is required for the operation of the whole system). For the maintenance of the system, the units to be supervised are equipped with control circuits, which indicate whether the unit is in the normal operating condition or not. The control data are transferred to the control unit, which can be situated beside the units to be supervised or somewhere at a distance. The purpose of the control unit is to give the actual alarm and help to determine the alarm class. The alarm class indicates how urgent maintenance the failure requires.

With regard to cabling, the following methods of transferring the control data are known:

1) There is a separate cable to the control unit from each unit to be supervised. The error data are then received separately from each unit, and the class that shows the urgency of the alarm can be determined immediately. The method has the drawback of relatively high cabling costs.

2) There is a common cable from the units to be supervised to the control unit. Some of the cable wires are reserved for each unit, and some of them are common for all units. The reserved wires provide error data from each unit. Generally, however, most of the error data are transferred by wires that are used commonly. Common use means that there is one pair of wires for each type of failure. The method has the advantage that cabling costs are low. On the other hand, it has the drawback that when a failure occurs it is not known whether the failure is in one or more units, because in both cases there is a similar alarm. Because of the inaccuracy of the alarm information it is not known how urgent maintenance is needed in each case.

The purpose of the invention is to eliminate the above mentioned drawbacks. The method according to the invention is characterized in what is set forth in Claim 1.

The arrangement according to the invention is characterized in what is set forth in Claim 3. The preferred embodiments of the invention are described in the dependent claims.

The basic idea of the invention is the following: Each parallel rectifier unit is equipped with a simple power generator, which stops feeding the signalling current when a failure occurs. The power generators of different units are connected to the same line, in which the signalling currents are summed. The value of the current then indicates how many units are operational. The line leads to the control unit, where the value of the current is monitored and information of the number of operational units is received. If there is more than one function to be monitored in each device unit, and thus more than one type of failure, a dedicated line and power generators are arranged for each type of failure.

The invention has the advantage that when a failure occurs, each control unit can determine the urgency class of the alarm immediately, because in addition to the type of failure, it receives information of the number of operational units. For example, if only one unit has failed, there is not an immediate need to take maintenance action. In addition, the invention has the advantage that the costs of cabling between the control unit and the rectifier units remain relatively low.

In the following, a preferred embodiment of the invention will be described in more detail with reference to the accompanying drawings, in which

Figure 1 shows the power supply equipment as a block diagram,

Figure 2 shows an example of the arrangement according to the invention as a circuit diagram, and

Figure 3 shows the operating conditions of a circuit according to Figure 2 in cases of failure.

The equipment in Figure 1 includes a control unit 100, the power supply equipment 200 to be supervised, the storage battery 300 acting as power reserve, a system 400 using power, such as a node of a telecommunication network, a bus 500 used to transfer control data, and a connection to a three-phase power network 600. In this example, the power supply equipment 200 consists of five parallel rectifier units, particularly the rectifiers 210, 220, 230, 240, 250. In the method for supervising power supply equipment according to the invention, each rectifier unit 210, 220, 230, 240, 250 in the right operating condition is arranged to feed constant current as a unit-specific signal, the unit-specific constant currents are summed and the current signal thus formed is sent to the control unit 100, and the number of rectifier units 210, 220, 230, 240, 250 in the right operating condition is determined in the control unit 100 on the basis of the current signal.

The supervision arrangement according to the invention comprises circuits for transmitting the control data, 211, 221, 231, 241, 251, error detecting circuits 212, and a circuit for receiving the control data, 110. Each rectifier 210, 220, 230, 240, 250, correspondingly comprises a transmission circuit of its own 211 , 221 , 231 , 241 , 251 and a related detector 212, 222, 232, 242, 252.

Figure 2 illustrates the supervision arrangement according to the invention and its operation in the equipment shown in Figure 1. Of the control data transmission circuits 211, 221, 231, 241, 251, only two are shown in Figure 2, the first 211 and the last 251. The other transmission circuits have been implemented in the same way. Each of the transmission circuits 211, 221, 231, 241, 251 comprises a constant current generator implemented with a transistor Ql, ..., Q5 and a resistor Rl, ..., R5. Of the detectors 212, 222, 232, 242, 252, Figure 2 also shows only the first 212 and the last 252. Each detector 212, ..., 252 includes an alarm relay, of which only the coil Wl, ..., W5 and one contact kl, ..., k5 is shown in Figure 2. The contacts kl, ..., k5 of the alarm relays are used to control the power generators of the corresponding transmission circuits 211, 221, 231, 241, 251. For example, when the rectifier 210 is operational, the alarm relay of the detector 212 is stressed, whereby the contact kl is closed, and the transistor Ql of the transmission circuit 211 receives control current. The base B of the transistor Ql has the voltage -V_B = 3.3N formed by means of the resistor R6 and the zener diode ZD. The voltage difference between the emitter E and the base is approximately 0.7V when the transistor conducts, whereby the voltage of the emitter is approximately 4V. If the resistance of the resistor Rl is 1 kΩ, the current of the transistor Ql is Ii « (5-4) V/l kΩ = 1 mA. If the rectifier 210 is damaged, the alarm relay that is part of its detector 212 is released, whereby the contact kl is opened, the transistor Ql of the transmission circuit 211 stops conducting and the current l_λ drops to zero. The outputs of the transmission circuits 211, ..., 251 and thus the outputs of the power generators, or the collectors of the transistors are connected together, from which point there is a line 205 to the reception circuit 110 of the control unit 100. The total current I of the line 205 is the sum of all the currents I_l5 1₂, 1₃ 1₄, 1₅ of the transmission circuits 211, 221, 231, 241, 251. Thus the value of the current I in milliampers indicates the number of rectifiers 210, 220, 230, 240, 250 that are operational.

The reception circuit 110 of the control unit 100 in Figure 2 includes a current measurement resistor R7, five comparators 111, a resistor chain 112 and a logic unit 113. The resistor R7 is used to convert the current signal I into a voltage signal N. The capacitor C2 attenuates the spurious variations of the voltage N of the line 205. If the resistance of the resistor R7 is 600Ω, the current I_l5 I₂, I₃, I₄, I₅ of each transmission circuit 211, 221, 231, 241, 251 causes an addition of 0.6V to the voltage V. Thus the voltage V can be 0V, 0.6V, 1.2V, 1.8V, 2.4V or 3.0V depending on whether 1, 2, 3, 4 or 5 rectifiers are operational. The resistor chain 112 provides reference voltages V_rι=0.3V, V_r2=0.9V, V_r3=1.5V, V_r4=2.1V and V_r5=2.7V in the middle of the above mentioned voltage signal values. The comparators 111 (a, b, c, d and e) indicate in which range the value of the voltage V is. If, for example, three rectifiers are operational, the nominal value of the voltage V is 1.8V, whereby the comparators a, b and c give the upper voltage (=" 1 ") and the comparators d and e give the lower voltage (="0"). The comparators give the correct voltage levels if the voltage V is in the range 1.5 V - 2.1V. Thus the tolerance of the voltage V is +0.3 V, which is 10% of the whole range of variation 3 V. The outputs of the comparators 111 are connected to the logic unit 113, which comprises a buffer f, AΝD-gates g, h, i and j, and a NOT- gate k. In the figure showing the AND- gates, the lower input is inverting. The logic unit 113 gives the output signals DO, D2, D3, D4, D5. If none of the rectifiers is operational, DO = " 1" and the other outputs are in the state "0". If one rectifier is operational, only Dl = "1 " and the other outputs are in the state "0". If for instance four rectifiers are operational, only D4 = " 1 " and the other outputs are in the state "0".

Figure 3 shows an example of the setting of the output signals DO, D2, D3, D4, D5. At first, all rectifiers 210, 220, 230, 240, 250 are operational, whereby the current 1=3 mA, the voltage V=3.0V, and of the output signals only D5=" l ". At the moment t_h one rectifier is damaged. A contact of the alarm relay is opened in the detector circuit of the rectifier, whereby the transistor controlled by it becomes nonconducting, and the current I and the voltage V drop by one step. After that, of the output signals only D4=" l". At the moment t₂, two more rectifiers are damaged at the same time. The current I and the voltage V drop by two more steps, and after that of the output signals only D2="l". An example of the transfer of control data according to the invention was described above. The invention is not limited to the circuit solutions described only. For example, the current signal can be arranged so that it has a base value other than zero, when all the units being supervised are damaged. It is also possible, if the control unit is processor-based, to leave out the logic unit 113 and take the output signals of the comparators 111 directly to the processor.

Claims

1. A method for supervising power supply equipment (200) comprising parallel rectifier units (210, 220, 230, 240, 250), in which method there is a connection from the rectifier units being supervised to a control unit (100) and the operating condition of each rectifier unit is monitored, characterized in that

- each rectifier unit (210, 220, 230, 240, 250) in the right operating condition feeds a constant current (I_ls I₂, 1₃, 1₄, 1₅) as a unit-specific signal,

- the unit-specific constant currents (Ii, I₂, I₃, I , I₅) are summed and the current signal (I) thus formed is sent to the control unit, and

- the number of rectifier units in the right operating condition is determined in the control unit (100) on the basis of the current signal (I).

2. A method according to Claim I, characterized in that each rectifier unit being supervised (210, 220, 230, 240, 250) feeds a signal current separately for each feature of the rectifer being monitored, such as its operating condition, reception of supply voltage, the suitability of the direct voltage and/or the loading.

3. An arrangement for supervising power supply equipment (200) comprising parallel rectifier units (210, 220, 230, 240, 250), in which arrangement there are signal lines (500) from the units being supervised to the control unit (100), and the operating condition of each unit being supervised is monitored, characterized in that

- each rectifier unit (210, 220, 230, 240, 250) includes a detector (212, 222, 232, 242, 252) and a transmission circuit (211, 221, 231, 241, 251), which is arranged to feed a constant current (I_l5 I₂, I₃, I , I₅) as a unit-specific signal when it is in the right operating condition according to the detector,

- the transmission circuits (211, 221, 231, 241, 251) of the rectifier units (210, 220, 230, 240, 250) are connected to the same signal line (500; 205), in which the currents (I., I₂, 1₃, 1 , 1₅) fed by said units are summed into a current signal (I) passing through the control unit (100), and - the control unit (100) includes a reception circuit (110, in which the information (DO, Dl, D2, D3, D4, D5) that indicates the number of units in the right operating condition is formed.

4. An arrangement according to Claim 3, characterized in that each of the rectifier units being supervised (210, 220, 230, 240, 250) includes a number of detectors (e.g. 212) and transmission circuits (e.g. 211), each of which is arranged to feed a constant current (e.g. 1 when the function monitored by the relevant detector is in order.

5. An arrangement according to Claim 3 or 4, characterized in that the transmission circuit (e.g. 211) includes a current generator, which is preferably implemented by means of a transistor (e.g. Ql) and a resistor (e.g. Rl).

6. An arrangement according to Claim 3, 4 or 5, characterized in that the reception circuit (110) comprises

- a current-to-voltage transducer, preferably a resistor (R7) for transforming the current signal (I) into a voltage signal (V),

- a resistor chain (112), which produces reference voltages (V_r], V_r2, V_r3, V_r4, V_r5) from the operating voltage (+5V) to the voltage signal (V), and

- a number of comparators (111 a, b, c, d, e) corresponding to the number of transmission circuits (211, 221, 231, 241, 251), the first inputs of which receive the voltage signal (V) and the second inputs receive said reference voltages, and the output signals of which indicate how many of the rectifier units (210, 220, 230, 240, 250) are in the right operating condition.

7. An arrangement according to Claim 6, characterized in that the reception circuit (110) comprises a logic unit (113), which is controlled by the output signals of the comparators (11 la, b, c, d, e) and of the output signals of which (DO, Dl, D2, D3, D4, D5) the active signal indicates the number of rectifier units (210, 220, 230, 240, 250) being supervised that are in the right operating condition.

8. An arrangement according to any one of the preceding claims 3 to 7, characterized in that the transmission link (500) includes a pair of conductors (205) for each feature being monitored in the rectifier units (210, 220, 230, 240, 250).