AS/NZS 1802 is the Australian and New Zealand standard that specifies construction and testing requirements for reeling and trailing cables specifically designed for use in underground coal mines.¹ These cables are engineered to withstand the harsh environmental conditions found in mining operations, including mechanical stress, moisture, and potential exposure to hazardous atmospheres. The standard aligns with AS/NZS 2802 for cables developed to meet the special requirements of the surface mining industry and introduces critical safety features including earth fault screens and central pilot cores.¹

AS/NZS 1802 是澳大利亚和新西兰标准,规定了专门用于地下煤矿的卷筒电缆和拖曳电缆的结构和测试要求。这些电缆经过设计,能够承受采矿作业中的恶劣环境条件,包括机械应力、湿度以及可能接触危险气体。

Many AS/NZS 1802 cable types incorporate a central pilot core as an integral component of their construction. According to the standard, central pilot cores or control cores are specified for certain cable types including Types 209, 210, 241, 245, 275, and 280B.¹ The pilot core typically consists of a flexible stranded tinned annealed copper conductor covered with EPR (Ethylene Propylene Rubber) insulation, designed to be extensible to accommodate the cable’s movement during operation.²

许多 AS/NZS 1802 电缆类型包含中央导引芯作为其结构的组成部分。根据标准,中央导引芯或控制芯规定用于某些电缆类型,包括 209、210、241、245、275 和 280B 型。

The central placement of this pilot core within the cable assembly is strategically important. In asymmetric cable designs where the pilot core is not centrally located among the three power cores, there can be increased susceptibility to electromagnetic interference and induced voltages, which can affect the reliability of the earth continuity monitoring system.³

导引芯在电缆组件中的中心位置具有战略重要性。在导引芯未位于三个电力芯中心的非对称电缆设计中,可能增加对电磁干扰和感应电压的敏感性。

The central pilot core serves a critical safety function in mining cable installations by enabling earth continuity protection through what is known as pilot earth loop or earth continuity monitoring.⁴ This protection method is fundamental to ensuring personnel safety in underground mining environments where electrical faults can create life-threatening hazards.

中央导引芯在采矿电缆装置中发挥着关键的安全功能,通过被称为导引接地回路或接地连续性监测的方式实现接地连续性保护。这种保护方法对于确保地下采矿环境中的人员安全至关重要。

Earth continuity protection operates by establishing a monitoring circuit through the pilot core. The system monitors a low voltage DC signal applied between the pilot core and the earth conductor of the cable, measuring the resistance of this pilot-earth loop.³ Earth continuity monitoring devices, which must comply with AS/NZS 2081 requirements, continuously check that the earth connection through trailing or reeling cables is maintained.⁵

接地连续性保护通过导引芯建立监测电路来运行。系统监测施加在导引芯和电缆接地导体之间的低压直流信号,测量该导引-接地回路的电阻。

In a typical implementation, the pilot cable is connected to earth via a diode at the equipment end. The earth continuity relay detects both open circuits and short circuits between the pilot and earth conductors of the trailing cables.⁵ The relay establishes a loop current through its operating coil, the pilot core, pilot switch, rectifier, and the earth core of the cable back to the supply transformer, which allows the three-phase contactor to close and energise the equipment.⁶

在典型实现中,导引电缆在设备端通过二极管连接到接地。接地连续性继电器检测导引和拖曳电缆接地导体之间的开路和短路。

The pilot core’s function is intrinsically linked to protecting personnel from hazardous touch potentials. When an earth fault occurs in mobile mining equipment powered by a trailing cable, earth fault current flows through the fault to the machine frame and returns to the supply transformer via the cable’s earth conductors. This current flow through the earth impedance creates a voltage drop, resulting in a potential rise of the equipment frame above earth potential, which presents the touch potential hazard.⁷

导引芯的功能与保护人员免受危险接触电位密切相关。当拖曳电缆供电的移动采矿设备发生接地故障时,接地故障电流通过故障流向机器框架,并通过电缆的接地导体返回供电变压器。

The earth continuity monitoring system must be coordinated with the installation’s earth fault impedance to disconnect quickly enough to prevent touch voltage from reaching hazardous levels.⁷ According to AS/NZS 4871.1:2012 standards for 50 Hz touch voltages, there are specific time-voltage curves that define safe exposure limits. Modern earth continuity relays like the ECM3 can adjust trip points from 15 ohms to 90 ohms in 5 ohm increments, with the ability to set thresholds close to the pilot resistance to ensure maximum touch voltage is kept within acceptable ranges.³

接地连续性监测系统必须与装置的接地故障阻抗相协调,以足够快地断开,防止接触电压达到危险水平。根据 AS/NZS 4871.1:2012 标准,存在定义安全暴露限值的特定时间-电压曲线。

Beyond earth continuity monitoring, central pilot cores in some cable configurations serve dual purposes by also accommodating control circuits.² In peripheral longwall cables, for instance, cables may have three central pilots designated for both earth continuity monitoring and control circuit functions. This design integration allows for efficient use of cable conductors while maintaining critical safety monitoring capabilities.

除了接地连续性监测之外,某些电缆配置中的中央导引芯还通过容纳控制电路来发挥双重作用。例如,在周边长壁电缆中,电缆可能具有三个指定用于接地连续性监测和控制电路功能的中央导引芯。

The implementation of central pilot cores and their associated earth continuity monitoring systems must comply with multiple Australian and New Zealand standards. AS/NZS 2081:2011 sets out design, performance, manufacturing, and testing requirements for electrical protection devices for use in surface and underground mines and quarries where IT (impedance earthed) supply networks are utilised.⁸ This standard provides comprehensive information on general principles of earth fault current limitation, earth continuity protection, earth fault protection, earth fault lockout protection, and neutral earthing resistor integrity protection.

中央导引芯及其相关接地连续性监测系统的实施必须符合多个澳大利亚和新西兰标准。AS/NZS 2081:2011 规定了用于地表和地下矿山和采石场的电气保护装置的设计、性能、制造和测试要求。

Earth continuity monitoring devices must meet specific requirements to monitor pilot-earth loops in cables supplying power to equipment, with the capability to initiate tripping to prevent closure or cause interruption of circuit devices when earth continuity is compromised.⁹ These requirements ensure that protection systems can respond appropriately to maintain personnel safety while minimising nuisance tripping that could unnecessarily interrupt mining operations.

接地连续性监测设备必须满足特定要求,以监测向设备供电的电缆中的导引-接地回路,当接地连续性受损时,能够启动跳闸以防止闭合或引起电路装置中断。

In actual mining installations, several factors affect the performance of pilot core earth continuity systems. Cable length significantly impacts the resistance of both the pilot and earth return paths, with longer cables presenting higher impedances that must be accounted for in protection system settings.⁷ Temperature variations can cause changes in pilot cable resistance, requiring earth continuity relays to compensate for these dynamic conditions while avoiding false trips.

在实际采矿装置中,多种因素影响导引芯接地连续性系统的性能。电缆长度显著影响导引和接地回路路径的电阻,较长的电缆呈现更高的阻抗。

Electromagnetic noise coupled onto the pilot conductor represents another challenge, particularly in environments with multiple high-power electrical systems operating in proximity. Advanced earth continuity relays incorporate filtering mechanisms to remove unwanted inductively or capacitively coupled AC signals while maintaining accurate resistance measurements.⁵ Modern protection relays can operate continuously even when exposed to voltages up to 40 volts AC on the pilot core, with thermal overload protection engaging only when higher induced voltages are present.³

耦合到导引导体上的电磁噪声代表另一个挑战,特别是在多个高功率电气系统邻近运行的环境中。先进的接地连续性继电器结合过滤机制,以消除不需要的感应或容性耦合的交流信号。

The central pilot core in AS/NZS 1802 cables represents a fundamental safety feature for underground mining operations. By providing continuous monitoring of earth continuity, these pilot cores enable protection systems to detect earth conductor failures before personnel can be exposed to hazardous touch potentials during electrical faults. The integration of pilot core monitoring with modern earth continuity relays creates a comprehensive protection scheme that balances personnel safety with operational reliability, ensuring that mining equipment can operate safely while maintaining the productivity essential to mining operations.

AS/NZS 1802 电缆中的中央导引芯代表地下采矿作业的基本安全特征。通过提供接地连续性的连续监测,这些导引芯使保护系统能够在电气故障期间人员暴露于危险接触电位之前检测到接地导体故障。