NZ764588B2

NZ764588B2 - An electromagnetic frequency (emf) detecting safety shovel for detecting the presence of subsurface power cables during excavation

Info

Publication number: NZ764588B2
Application number: NZ764588A
Authority: NZ
Inventors: Brenton Davey
Original assignee: Brp Group Pty Ltd
Filing date: 2018-11-06
Publication date: 2025-09-02

Abstract

EMF detecting safety shovel has electromagnetic field (EMF) detection circuitry operably coupled to an indicator and an antenna formed by a blade or being attached to the blade thereof for measuring changes in EMF over time (AC fields) and providing an indication, which are used by spotters during excavation work for detection of subsurface power supply cables. The safety shovel is further configured for classifying different types of subsurface power cables wherein the EMF detector circuit employs at least one bandpass filter wherein the at least one bandpass filter comprises a bandpass window at a single phase supply frequency and a second bandpass window at a three phase supply frequency approximately three times the single phase supply frequency and wherein, in use, the bandpass filter is operably coupled to the indicator to provide single and three phase indications accordingly. In this way, the present safety shovel provides indication of the presence of subsurface power supply cables and also the type thereof.

Claims

1. An EMF detecting safety shovel comprising: a handle; a blade at a g end of the handle; EMF detection circuity comprising: an a formed by the blade or being attached to the blade; an EMF detector circuit operably coupled to the antenna; and an tor operably coupled to the EMF detector circuit, wherein, in use, the indicator provides an indication of the ion of EMF of a subsurface power cable wherein the EMF detector circuit comprises at least one bandpass filter, wherein the at least one bandpass filter comprises a bandpass window at a single phase supply frequency and a second bandpass window at a three phase supply frequency approximately three times the single phase supply frequency and wherein, in use, the bandpass filter is ly coupled to the indicator to provide single and three phase indications accordingly.

2. An EMF detecting safety shovel as claimed in claim 1, wherein the EMF detector circuit comprises a level sensor configured for discriminating between low and high voltages of the subsurface power cable and wherein the level sensor is operably coupled to the indicator to provide low and high voltage indications accordingly.

3. An EMF detecting safety shovel as claimed in claim 2, wherein the level sensor is ured for discriminating between low voltages being less than imately 1000 V and high voltages being r than imately 1000 V, wherein the EMF detector circuit is ured for discriminating between the low and high voltages when an edge of the blade is within a certain distance of the subsurface power cable in use.

4. An EMF detecting safety shovel as claimed in claim 3, wherein the distance is less than approximately 150 mm.

5. An EMF detecting safety shovel as claimed in claim 3, wherein a voltage discrimination threshold of the level sensor is configurable.

6. An EMF detecting safety shovel as claimed in claim 3, wherein an edge of the blade comprises a cutout for the partial receipt of the power cable therein for discriminating between the low and high es at a set distance and location with respect to the EMF detector t.

7. An EMF detecting safety shovel as claimed in claim 3, wherein the EMF detector circuit comprises an input operational amplifier operably coupled to the antenna and configured for outputting signals indicative of the strength of EMF picked up by the antenna.

8. An EMF ing safety shovel as claimed in claim 1, wherein the single phase supply frequency is approximately at least one of 50 Hz or 60 Hz and wherein the three phase supply frequency is approximately is one of 150 Hz or 180 Hz.

9. An EMF detecting safety shovel as claimed in claim 2, further comprising a digital controller acing the EMF detector circuit and the indicator, wherein an analogue to digital converter interfaces the EMF detection circuit and the digital controller , r comprising a memory device operably ted to the digital controller, wherein the memory device comprises a plurality of computer program code instruction modules for controlling the operation of the controller in use, wherein the computer program code instruction modules se a detector module.

10. An EMF detecting safety shovel as claimed in claim 9, wherein the detector module is configured for ing an EMF rm to discriminate between single and three phase supply.

11. An EMF detecting safety shovel as d in claim 9, wherein the detector module is configured for analysing an EMF waveform to discriminate between the low and high es.

12. An EMF detecting safety shovel as claimed in claim 9, wherein the computer program code instruction modules comprises a signaller module configured for controlling the indicator.

13. An EMF detecting safety shovel as claimed in claim 12, wherein the signaller module is configured for controlling the tor to indicate the detection of EMF.

14. An EMF detecting safety shovel as claimed in claim 12, n the signaller module is configured for controlling the indicator to indicate the detection of low or high voltage EMF.

15. An EMF detecting safety shovel as claimed in claim 12, wherein the signaller module is configured for controlling the indicator to indicate the detection of single phase or three-phase voltage EMF. 102 109 103 Light Antenna Amp Sound ss 105 Filter Blade 106 107 Level 111 A/D Controller Sensor Detector circuit 112 Signaller Detector Settings