This is simple code for pinging an address and save the results in a log file and can get percent about lost and success packets and then run your command when you got lost packets over 20%!

ping_log.sh

#!/bin/bash

#read -p "Enter your url: " $address

######
#	Ping URL and get percent
######

address='google.com'
log_file='packet.log'

### ./ping.sh ping
if [ "$1" == "ping" ];then
	check = $(ping $address -c1 > /dev/null 2>&1)
	if [ "$check" -ne "0" ]
	then
		echo "2," >> $log_file
	else
		echo "1," >> $log_file
	fi
fi

### ./ping.sh log "init 0"
### ./ping.sh log "mail ....."
if [ "$1" == "log" ];then
	#lost
	packet_false=$(grep 2 -o $log_file | wc -l)
	#success
	packet_true=$(grep 1 -o $log_file | wc -l)
	#total
	total_packet=$(($packet_false+$packet_true))
	
	p_f=$(($packet_false*100/$total_packet))
	p_t=$(($packet_true*100/$total_packet))
	echo "packet lost:" $p_f%
	echo "Packet Success:" $p_t%
	if [ "$p_f" -gt "20" ]
	then
		$2
	fi
fi

You can run it via Cron . For example ping every 10 minutes and check log file after 2 hours if the lost packets were over that 20% , then turn off the system.
10 * * * * /your/path/ping.sh ping

• 2 * * * /your/path/ping.sh log "init 0"